Moving picture coding device, moving picture coding method, and moving picture coding program, and moving picture decoding device, moving picture decoding method, and moving picture decoding program

ABSTRACT

A prediction information deriving unit derives the inter-prediction information candidates from inter-prediction information of a prediction block neighboring to a coding target prediction block or a prediction block present at the same position as or near the coding target prediction block in a coded picture at a temporally different position from the coding target prediction block. A candidate supplementing unit supplements inter-prediction information candidates having the same prediction mode, reference index, and motion vector until the number of inter-prediction information candidates reaches the designated number of candidates when the number of inter-prediction information candidates is smaller than the designated number of candidates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/479,139, filed Sep. 5, 2014, which is a Continuation of InternationalApplication No. PCT/JP2013/002513, filed Apr. 12, 2013, which claims thebenefit of Japanese Patent Application Nos. 2012-091385 and 2012-091386,filed Apr. 12, 2012, and 2013-083577 and 2013-083578, filed Apr. 12,2013.

BACKGROUND

1. Field of the Invention

The present invention relates to a technique of coding and decodingmoving pictures, and more particularly, to a technique of coding anddecoding moving pictures using motion-compensated prediction.

2. Description of the Related Art

The MPEG-4 AVC/H.264 standard is a representative moving picturecompression coding scheme. The MPEG-4 AVC/H.264 standard uses motioncompensation in which a picture is partitioned into a plurality ofrectangular blocks, pictures which have been coded or decoded are usedas reference pictures, and a motion is predicted from the referencepictures. A method of predicting a motion based on this motioncompensation is referred to as inter-prediction or motion-compensatedprediction. In the inter-prediction of the MPEG-4 AVC/H.264 standard,motion compensation is performed in such a manner that a plurality ofpictures can be used as reference pictures, and a most probablereference picture is selected in respective blocks from the plurality ofreference pictures. Thus, a reference index is allocated to respectivereference pictures and the reference pictures are specified by thereference index. In B pictures, two reference pictures at most can beselected from coded or decoded reference pictures and be used forinter-prediction. Prediction from these two reference pictures isclassified into L0 prediction (list-0 prediction) which is mainly usedas forward prediction and L1 prediction (list-1 prediction) which ismainly used as backward prediction.

Further, bi-prediction which uses two inter-prediction modes of L0prediction and L1 prediction simultaneously is also defined. In the caseof bi-prediction, bidirectional prediction is performed to obtaininter-prediction signals in L0 and L1 prediction modes, which aremultiplied by a weighting factor and are superimposed by adding anoffset value to thereby construct a final inter-prediction picturesignal. As the weighting factor and offset values used for weightedprediction, a representative value for each reference picture of listsis set and coded in respective pictures. Coding information related tointer-prediction includes a prediction mode for classifying L0prediction, L1 prediction, and bi-prediction for each block, a referenceindex for specifying a reference picture for each reference list of eachblock, and a motion vector representing a moving direction and amovement amount of a block. These items of coding information are codedor decoded.

Further, in the MPEG-4 AVC/H.264 scheme, a direct mode of constructinginter-prediction information of coding/decoding target block frominter-prediction information of a coded/decoded block is defined. Sincethe direct mode does not require coding of inter-prediction information,coding efficiency is improved.

A temporal direct mode which uses correlation of inter-predictioninformation in the temporal direction will be described with referenceto FIG. 36. A picture of which the L1 reference index is registered to“0” is referred to as a reference picture colPic. A block at the sameposition as a coding/decoding target block in the reference picturecolPic is referred to as a reference block.

If a reference block is coded using L0 prediction, a L0 motion vector ofthe reference block is referred to as a reference motion vector mvCol.If the reference block is not coded using L0 prediction but is codedusing L1 prediction, a L1 motion vector of the reference block isreferred to as a reference motion vector mvCol. A picture that thereference motion vector mvCol refers to is referred to as a L0 referencepicture of the temporal direct mode, and the reference picture colPic isreferred to as a L1 reference picture of the temporal direct mode.

A L0 motion vector mvL0 and a L1 motion vector mvL1 of the temporaldirect mode are derived from the reference motion vector mvCol byperforming a scaling process.

A POC of a L0 reference picture of the temporal direct mode issubtracted from a POC of the reference picture colPic to derive apicture-to-picture distance td. A POC is a variable associated with apicture to be coded and a value that is incremented by 1 in the pictureoutputting/displaying order is set as the POC. A difference between thePOCs of two pictures represents a picture-to-picture distance in a timeaxis direction.

td=(POC of reference picture colPic)−(POC of L0 reference picture oftemporal direct mode)

The POC of a L0 reference picture of the temporal direct mode issubtracted from the POC of a coding/decoding target picture to derive apicture-to-picture distance tb.

tb=(POC of coding/decoding target picture)−(POC of L0reference pictureof temporal direct mode)

A L0 motion vector mvL0 of the temporal direct mode is derived from thereference motion vector mvCol by performing a scaling process.

mvL0=tb/td*mvCol

A reference motion vector mvCol is subtracted from the L0 motion vectormvL0 of the temporal direct mode to derive a L1 motion vector mvL1.

mvL1=mvL0−mvCol

When a moving picture coding device and a moving picture decoding devicehave low processing capability, the process of the temporal direct modemay be omitted.

-   Patent Literature 1: JP 2004-129191 A

Under such a situation, the present inventors have recognized the needto further compress coding information and reduce an entire codingamount in a moving picture coding scheme which uses motion-compensatedprediction.

SUMMARY OF THE INVENTION

The present invention has been made in view of such a situation, and anobject thereof is to provide a moving picture coding and decodingtechnique of reducing a coding amount of coding information to improvecoding efficiency by deriving candidates for prediction information usedin motion-compensated prediction according to a situation.

In order to achieve the object, a moving picture coding device accordingto one aspect of the present invention is one codes moving picturesusing motion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, and the moving picturecoding device includes: a prediction information coding unit (110) thatcodes information indicating a designated number of inter-predictioninformation candidates; a prediction information deriving unit (104)that derives the inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; a candidate list constructing unit (130) thatconstructs an inter-prediction information candidate list from thederived inter-prediction information candidates; a candidatesupplementing unit (135) that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and a motion-compensatedprediction unit (105) that selects one inter-prediction informationcandidate from the inter-prediction information candidates included inthe inter-prediction information candidate list and performsinter-prediction on the coding target prediction block using theselected inter-prediction information candidate.

Another aspect of the present invention provides a moving picture codingdevice. The device is a moving picture coding device that codes movingpictures using motion-compensated prediction in units of blocks obtainedby partitioning each picture of the moving pictures, including: aprediction information coding unit (110) that codes informationindicating a designated number of inter-prediction informationcandidates; a prediction information deriving unit (104) that derivesthe inter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a coding targetprediction block or a prediction block present at the same position asor near the coding target prediction block in a coded picture at atemporally different position from the coding target prediction block; acandidate list constructing unit (130) that constructs aninter-prediction information candidate list from the derivedinter-prediction information candidates; a candidate adding unit (134)that derives inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the designated number of inter-predictioninformation candidates and adds the derived inter-prediction informationcandidates to the constructed inter-prediction information candidatelist and that derives one or a plurality of inter-prediction informationcandidates of which at least one of the prediction mode, the referenceindex, and the motion vector is changed from that of theinter-prediction information candidates having the predetermined valuewhen the number of inter-prediction information candidates included inthe added inter-prediction information candidate list is smaller thanthe designated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe added inter-prediction information candidate list; a candidatesupplementing unit (135) that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe additionally added inter-prediction information candidate list; anda motion-compensated prediction unit (105) that selects oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performs inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding device. The device is a moving picture coding device that codes abitstream obtained by coding moving pictures using motion-compensatedprediction in units of blocks obtained by partitioning each picture ofthe moving pictures, including: a prediction information coding unit(110) that codes information indicating a designated number ofinter-prediction information candidates; a prediction informationderiving unit (104) that derives the inter-prediction informationcandidates from inter-prediction information of a prediction blockneighboring to a coding target prediction block or a prediction blockpresent at the same position as or near the coding target predictionblock in a coded picture at a temporally different position from thecoding target prediction block; a candidate list constructing unit (130)that constructs an inter-prediction information candidate list from thederived inter-prediction information candidates; a candidatesupplementing unit (135) that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, that derives one or aplurality of inter-prediction information candidates of which theprediction mode and the motion vector have the same value as and thereference index is changed from that of the inter-prediction informationcandidates having the predetermined value when the number ofinter-prediction information candidates included in the addedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe added inter-prediction information candidate list, and that derivesinter-prediction information candidates of which the prediction mode,the reference index, and the motion vector have predetermined valuesuntil the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate listreaches the designated number of inter-prediction information candidateswhen the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate list issmaller than the designated number of inter-prediction informationcandidates and additionally adds the derived inter-predictioninformation candidates to the additionally added inter-predictioninformation candidate list; and a motion-compensated prediction unit(105) that selects one inter-prediction information candidate from theinter-prediction information candidates included in the inter-predictioninformation candidate list and performs inter-prediction on the codingtarget prediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding device. The device is a moving picture coding device that codesmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information deriving unit (104) that stores and initializesa designated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, derives inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; and a motion-compensated prediction unit (105) thatselects one inter-prediction information candidate from theinter-prediction information candidates included in the inter-predictioninformation candidate list and performs inter-prediction on the codingtarget prediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding device. The device is a moving picture coding device that codesmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information coding unit (110) that codes informationindicating a designated number of inter-prediction informationcandidates; a prediction information deriving unit (104) that derivesinter-prediction information candidates based on the number ofcandidates designated as the number of inter-prediction informationcandidates from inter-prediction information of a prediction blockneighboring to a coding target prediction block or a prediction blockpresent at the same position as or near the coding target predictionblock in a coded picture at a temporally different position from thecoding target prediction block; a candidate list constructing unit (130)that constructs an inter-prediction information candidate list from thederived inter-prediction information candidates; and amotion-compensated prediction unit (105) that selects oneinter-prediction information candidate from inter-prediction informationcandidates included in the inter-prediction information candidate listwhen the designated number of candidates is larger than or equal to 1and performs inter-prediction on the coding target prediction blockusing the selected inter-prediction information candidate and thatperforms inter-prediction of the coding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

Still another aspect of the present invention provides a moving picturecoding device. The device is a moving picture coding device that codesmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information deriving unit (104) that derivesinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a coding targetprediction block or a prediction block present at the same position asor near the coding target prediction block in a coded picture at atemporally different position from the coding target prediction block; acandidate supplementing unit (135) that supplements inter-predictioninformation candidates having the same prediction mode, reference index,and motion vector until the number of inter-prediction informationcandidates reaches the designated number of candidates when the numberof inter-prediction information candidates is smaller than thedesignated number of candidates; and a motion-compensated predictionunit (105) that selects one inter-prediction information candidate fromthe inter-prediction information candidates and performsinter-prediction of the coding target prediction block using theselected inter-prediction information candidate.

Still another aspect of the present invention is a moving picture codingmethod. The method is a moving picture coding method of coding movingpictures using motion-compensated prediction in units of blocks obtainedby partitioning each picture of the moving pictures, including: aprediction information coding step of coding information indicating adesignated number of inter-prediction information candidates; aprediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block; a candidate list constructingstep of constructing an inter-prediction information candidate list fromthe derived inter-prediction information candidates; a candidatesupplementing step of deriving inter-prediction information candidatesof which the prediction mode, the reference index, and the motion vectorhave predetermined values until the number of inter-predictioninformation candidates included in the inter-prediction informationcandidate list reaches the designated number of inter-predictioninformation candidates when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the designated number of inter-predictioninformation candidates and adding the derived inter-predictioninformation candidates to the constructed inter-prediction informationcandidate list; and a motion-compensated prediction step of selectingone inter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding method. The method is a moving picture coding method of codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates; a prediction information deriving step of deriving theinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a coding targetprediction block or a prediction block present at the same position asor near the coding target prediction block in a coded picture at atemporally different position from the coding target prediction block; acandidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; a candidate adding step of deriving inter-predictioninformation candidates of which the prediction mode, the referenceindex, and the motion vector have predetermined values when the numberof inter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list; a candidate supplementingstep of deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values until the number of inter-prediction informationcandidates included in the additionally added inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and a motion-compensated prediction step of selecting oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding method. The method is a moving picture coding method of coding abitstream obtained by coding moving pictures using motion-compensatedprediction in units of blocks obtained by partitioning each picture ofthe moving pictures, including: a prediction information number codingstep of coding information indicating a designated number ofinter-prediction information candidates; a prediction informationderiving step of deriving the inter-prediction information candidatesfrom inter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; a candidate list constructing step of constructing aninter-prediction information candidate list from the derivedinter-prediction information candidates; a candidate supplementing stepof deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the designated number of inter-predictioninformation candidates and adding the derived inter-predictioninformation candidates to the constructed inter-prediction informationcandidate list, deriving one or a plurality of inter-predictioninformation candidates of which the prediction mode and the motionvector have the same value as and the reference index is changed fromthat of the inter-prediction information candidates having thepredetermined value when the number of inter-prediction informationcandidates included in the added inter-prediction information candidatelist is smaller than the designated number of inter-predictioninformation candidates and additionally adds the derivedinter-prediction information candidates to the added inter-predictioninformation candidate list, and deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and a motion-compensated prediction step of selecting oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding method. The method is a moving picture coding method of codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information deriving step of storing and initializing adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, deriving inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; and a motion-compensated prediction step of selectingone inter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturecoding method. The method is a moving picture coding method of codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates; a prediction information deriving step of derivinginter-prediction information candidates based on the number ofcandidates designated as the number of inter-prediction informationcandidates from inter-prediction information of a prediction blockneighboring to a coding target prediction block or a prediction blockpresent at the same position as or near the coding target predictionblock in a coded picture at a temporally different position from thecoding target prediction block; a candidate list constructing step ofconstructing an inter-prediction information candidate list from thederived inter-prediction information candidates; and amotion-compensated prediction step of selecting one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate and performinginter-prediction of the coding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

Still another aspect of the present invention provides a transmitter.The transmitter includes: a packet processor that packetizes a bitstreamcoded according to a moving picture coding method of coding movingpictures using motion-compensated prediction in units of blocks obtainedby partitioning each picture of the moving pictures to obtain thepacketized bitstream; and a transmitting unit that transmits thepacketized bitstream. The moving picture coding method includes: aprediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates; a prediction information deriving step of deriving theinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a coding targetprediction block or a prediction block present at the same position asor near the coding target prediction block in a coded picture at atemporally different position from the coding target prediction block; acandidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; a candidate adding step of deriving inter-predictioninformation candidates of which the prediction mode, the referenceindex, and the motion vector have predetermined values when the numberof inter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list; a candidate supplementingstep of deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values until the number of inter-prediction informationcandidates included in the additionally added inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and a motion-compensated prediction step of selecting oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a transmissionmethod. The method includes: a packet processing step of packetizing abitstream coded according to a moving picture coding method of codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures to obtainthe packetized bitstream; and a transmitting step of transmitting thepacketized bit stream. The moving picture coding method includes: aprediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates; a prediction information deriving step of deriving theinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a coding targetprediction block or a prediction block present at the same position asor near the coding target prediction block in a coded picture at atemporally different position from the coding target prediction block; acandidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; a candidate adding step of deriving inter-predictioninformation candidates of which the prediction mode, the referenceindex, and the motion vector have predetermined values when the numberof inter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list; a candidate supplementingstep of deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values until the number of inter-prediction informationcandidates included in the additionally added inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and a motion-compensated prediction step of selecting oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the coding targetprediction block using the selected inter-prediction informationcandidate.

A moving picture decoding device according to an aspect of the presentinvention is a moving picture decoding device that decodes a bitstreamobtained by coding moving pictures using motion-compensated predictionin units of blocks obtained by partitioning each picture of the movingpictures, including: a prediction information decoding unit (202) thatdecodes information indicating a previously designated number ofinter-prediction information candidates; a prediction informationderiving unit (205) that derives the inter-prediction informationcandidates from inter-prediction information of a prediction blockneighboring to a decoding target prediction block or a prediction blockpresent at the same position as or near the decoding target predictionblock in a decoded picture at a temporally different position from thedecoding target prediction block; a candidate list constructing unit(230) that constructs an inter-prediction information candidate listfrom the derived inter-prediction information candidates; a candidatesupplementing unit (235) that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the previously designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand adds the derived inter-prediction information candidates to theconstructed inter-prediction information candidate list; and amotion-compensated prediction unit (206) that selects oneinter-prediction information candidate from the inter-predictioninformation candidates and performs inter-prediction on the decodingtarget prediction block using the selected inter-prediction informationcandidate.

Another aspect of the present invention provides a moving picturedecoding device. The device is a moving picture decoding device thatdecodes a bitstream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information decoding unit (202) that decodes informationindicating a previously designated number of inter-predictioninformation candidates; a prediction information deriving unit (205)that derives the inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; a candidate list constructing unit (230) thatconstructs an inter-prediction information candidate list from thederived inter-prediction information candidates; a candidate adding unit(234) that derives inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the designated number of inter-predictioninformation candidates and adds the derived inter-prediction informationcandidates to the constructed inter-prediction information candidatelist and that derives one or a plurality of inter-prediction informationcandidates of which at least one of the prediction mode, the referenceindex, and the motion vector is changed from that of theinter-prediction information candidates having the predetermined valuewhen the number of inter-prediction information candidates included inthe added inter-prediction information candidate list is smaller thanthe designated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe added inter-prediction information candidate list; a candidatesupplementing unit (235) that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the previouslydesignated number of inter-prediction information candidates when thenumber of inter-prediction information candidates included in theadditionally added inter-prediction information candidate list issmaller than the previously designated number of inter-predictioninformation candidates and additionally adds the derivedinter-prediction information candidates to the additionally addedinter-prediction information candidate list; and a motion-compensatedprediction unit (206) that selects one inter-prediction informationcandidate from the inter-prediction information candidates and performsinter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

Still another aspect of the present invention provides a moving picturedecoding device. The device is a moving picture decoding device thatdecodes a bitstream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information decoding unit (202) that decodes informationindicating a previously designated number of inter-predictioninformation candidates; a prediction information deriving unit (205)that derives the inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; a candidate list constructing unit (230) thatconstructs an inter-prediction information candidate list from thederived inter-prediction information candidates; a candidatesupplementing unit (235) that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand adds the derived inter-prediction information candidates to theconstructed inter-prediction information candidate list, that derivesone or a plurality of inter-prediction information candidates of whichthe prediction mode and the motion vector have the same value as and thereference index is changed from that of the inter-prediction informationcandidates having the predetermined value when the number ofinter-prediction information candidates included in the addedinter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand additionally adds the derived inter-prediction informationcandidates to the added inter-prediction information candidate list, andthat derives inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values until the number of inter-prediction informationcandidates included in the additionally added inter-predictioninformation candidate list reaches the previously designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand additionally adds the derived inter-prediction informationcandidates to the additionally added inter-prediction informationcandidate list; and a motion-compensated prediction unit (206) thatselects one inter-prediction information candidate from theinter-prediction information candidates and performs inter-prediction onthe decoding target prediction block using the selected inter-predictioninformation candidate.

Still another aspect of the present invention provides a moving picturedecoding device. The device is a moving picture decoding device thatdecodes a bitstream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information decoding unit (202) that decodes a designatednumber of inter-prediction information candidates; a predictioninformation deriving unit (205) that stores and initializes a designatednumber of inter-prediction information candidates having predeterminedprediction mode, reference index, and motion vector in advance in aninter-prediction information candidate list in which the designatednumber of inter-prediction information candidates are stored, and then,derives inter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a decoding targetprediction block or a prediction block present at the same position asor near the decoding target prediction block in a decoded picture at atemporally different position from the decoding target prediction block;and a motion-compensated prediction unit (206) that selects oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performs inter-prediction on the decoding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturedecoding device. The device is a moving picture coding device that codesmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information decoding unit (202) that decodes informationindicating a previously designated number of inter-predictioninformation candidates; a prediction information deriving unit (205)that derives inter-prediction information candidates based on the numberof candidates designated as the number of inter-prediction informationcandidates from inter-prediction information of a prediction blockneighboring to a decoding target prediction block or a prediction blockpresent at the same position as or near the decoding target predictionblock in a decoded picture at a temporally different position from thedecoding target prediction block; a candidate list constructing unit(230) that constructs an inter-prediction information candidate listfrom the derived inter-prediction information candidates; and amotion-compensated prediction unit (206) that selects oneinter-prediction information candidate from inter-prediction informationcandidates included in the inter-prediction information candidate listwhen the previously designated number of candidates is larger than orequal to 1 and performs inter-prediction on the decoding targetprediction block using the selected inter-prediction informationcandidate and that performs inter-prediction on the decoding targetprediction block using inter-prediction information having apredetermined value when the previously designated number of candidatesis 0.

Still another aspect of the present invention provides a moving picturedecoding device. The device is a moving picture decoding device thatdecodes a bitstream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information deriving unit (205) that derives inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block; a candidate supplementingunit (235) that supplements inter-prediction information candidateshaving the same prediction mode, reference index, and motion vectorvalues until the number of inter-prediction information candidatesreaches the designated number of candidates when the number ofinter-prediction information candidates is smaller than the designatednumber of candidates; and a motion-compensated prediction unit (206)that selects one inter-prediction information candidate from theinter-prediction information candidates and performs inter-prediction onthe decoding target prediction block using the selected inter-predictioninformation candidate.

Still another aspect of the present invention provides a moving picturedecoding method. The method is a moving picture decoding method ofdecoding a bit stream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information decoding step of decoding information indicatinga previously designated number of inter-prediction informationcandidates; a prediction information deriving step of deriving theinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a decoding targetprediction block or a prediction block present at the same position asor near the decoding target prediction block in a decoded picture at atemporally different position from the decoding target prediction block;a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; a candidate supplementing step of deriving inter-predictioninformation candidates of which the prediction mode, the referenceindex, and the motion vector have predetermined values until the numberof inter-prediction information candidates included in theinter-prediction information candidate list reaches the previouslydesignated number of inter-prediction information candidates when thenumber of inter-prediction information candidates included in theconstructed inter-prediction information candidate list is smaller thanthe previously designated number of inter-prediction informationcandidates and adding the derived inter-prediction informationcandidates to the constructed inter-prediction information candidatelist; and a motion-compensated prediction step of selecting oneinter-prediction information candidate from the inter-predictioninformation candidates and performing inter-prediction on the decodingtarget prediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturedecoding method. The method is a moving picture decoding method ofdecoding a bit stream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates; a prediction information deriving step ofderiving the inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; a candidate list constructing step ofconstructing an inter-prediction information candidate list from thederived inter-prediction information candidates; a candidate adding stepof deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the previously designated number ofinter-prediction information candidates and adding the derivedinter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the previously designatednumber of inter-prediction information candidates and additionallyadding the derived inter-prediction information candidates to the addedinter-prediction information candidate list; a candidate supplementingstep of deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values until the number of inter-prediction informationcandidates included in the additionally added inter-predictioninformation candidate list reaches the previously designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand additionally adding the derived inter-prediction informationcandidates to the additionally added inter-prediction informationcandidate list; and a motion-compensated prediction step of selectingone inter-prediction information candidate from the inter-predictioninformation candidates and performing inter-prediction on the decodingtarget prediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturedecoding method. The method is a moving picture decoding method ofdecoding a bit stream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates; a prediction information deriving step ofderiving the inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; a candidate list constructing step ofconstructing an inter-prediction information candidate list from thederived inter-prediction information candidates; a candidate adding stepof deriving inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the previously designated number ofinter-prediction information candidates and adding the derivedinter-prediction information candidates to the constructedinter-prediction information candidate list, deriving one or a pluralityof inter-prediction information candidates of which the prediction modeand the motion vector have the same value as and the reference index ischanged from that of the inter-prediction information candidates havingthe predetermined value when the number of inter-prediction informationcandidates included in the added inter-prediction information candidatelist is smaller than the previously designated number ofinter-prediction information candidates and additionally adds thederived inter-prediction information candidates to the addedinter-prediction information candidate list, and derivinginter-prediction information candidates of which the prediction mode,the reference index, and the motion vector have predetermined valuesuntil the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate listreaches the previously designated number of inter-prediction informationcandidates when the number of inter-prediction information candidatesincluded in the additionally added inter-prediction informationcandidate list is smaller than the previously designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the additionallyadded inter-prediction information candidate list; and amotion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesand performing inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

Still another aspect of the present invention provides a moving picturedecoding method. The method is a moving picture decoding method ofdecoding a bit stream obtained by coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, including: aprediction information number decoding step of decoding a designatednumber of inter-prediction information candidates; a predictioninformation deriving step of storing and initializing a designatednumber of inter-prediction information candidates having predeterminedprediction mode, reference index, and motion vector in advance in aninter-prediction information candidate list in which the designatednumber of inter-prediction information candidates are stored, and then,deriving inter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a decoding targetprediction block or a prediction block present at the same position asor near the decoding target prediction block in a decoded picture at atemporally different position from the decoding target prediction block;and a motion-compensated prediction step of selecting oneinter-prediction information candidate from the inter-predictioninformation candidates included in the inter-prediction informationcandidate list and performing inter-prediction on the decoding targetprediction block using the selected inter-prediction informationcandidate.

Still another aspect of the present invention provides a moving picturedecoding method. The method is a moving picture coding method of codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, including:a prediction information decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates; a prediction information deriving step ofderiving inter-prediction information candidates based on the number ofcandidates designated as the number of inter-prediction informationcandidates from inter-prediction information of a prediction blockneighboring to a decoding target prediction block or a prediction blockpresent at the same position as or near the decoding target predictionblock in a decoded picture at a temporally different position from thedecoding target prediction block; a candidate list constructing step ofconstructing an inter-prediction information candidate list from thederived inter-prediction information candidates; and amotion-compensated prediction step of selecting one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thepreviously designated number of candidates is larger than or equal to 1and performing inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate and performinginter-prediction on the decoding target prediction block usinginter-prediction information having a predetermined value when thepreviously designated number of candidates is 0.

Another aspect of the present invention provides a receiver. Thereceiver is a receiver that receives and decodes a bitstream obtained bycoding moving pictures, including: a receiving unit that receives abitstream obtained by packetizing a bitstream obtained by coding movingpictures using motion-compensated prediction in units of blocks obtainedby partitioning each picture of the moving pictures; a reconstructingunit that packetizing the received bitstream to reconstruct an originalbitstream; a prediction information decoding unit (202) that decodesinformation indicating a previously designated number ofinter-prediction information candidates from the reconstructedbitstream; a prediction information deriving unit (205) that derives theinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a decoding targetprediction block or a prediction block present at the same position asor near the decoding target prediction block in a decoded picture at atemporally different position from the decoding target prediction block;a candidate list constructing unit (230) that constructs aninter-prediction information candidate list from the derivedinter-prediction information candidates; a candidate adding unit (234)that derives inter-prediction information candidates of which theprediction mode, the reference index, and the motion vector havepredetermined values when the number of inter-prediction informationcandidates included in the constructed inter-prediction informationcandidate list is smaller than the previously designated number ofinter-prediction information candidates and adds the derivedinter-prediction information candidates to the constructedinter-prediction information candidate list and that derives one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the previously designatednumber of inter-prediction information candidates and additionally addsthe derived inter-prediction information candidates to the addedinter-prediction information candidate list; a candidate supplementingunit (235) that derives inter-prediction information candidates of whichthe prediction mode, the reference index, and the motion vector havepredetermined values until the number of inter-prediction informationcandidates included in the additionally added inter-predictioninformation candidate list reaches the previously designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand additionally adds the derived inter-prediction informationcandidates to the additionally added inter-prediction informationcandidate list; and a motion-compensated prediction unit (206) thatselects one inter-prediction information candidate from theinter-prediction information candidates and performs inter-prediction onthe decoding target prediction block using the selected inter-predictioninformation candidate.

Another aspect of the present invention provides a reception method. Themethod is a reception method of receiving and decoding a bitstreamobtained by coding moving pictures, including: a receiving step ofreceiving a bitstream obtained by packetizing a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures; areconstructing step of packetizing the received bitstream to reconstructan original bitstream; a prediction information decoding step ofdecoding information indicating a previously designated number ofinter-prediction information candidates from the reconstructed bitstream; a prediction information deriving step of deriving theinter-prediction information candidates from inter-predictioninformation of a prediction block neighboring to a decoding targetprediction block or a prediction block present at the same position asor near the decoding target prediction block in a decoded picture at atemporally different position from the decoding target prediction block;a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; a candidate adding step of deriving inter-predictioninformation candidates of which the prediction mode, the referenceindex, and the motion vector have predetermined values when the numberof inter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand adding the derived inter-prediction information candidates to theconstructed inter-prediction information candidate list, and derivingone or a plurality of inter-prediction information candidates of whichat least one of the prediction mode, the reference index, and the motionvector is changed from that of the inter-prediction informationcandidates having the predetermined value when the number ofinter-prediction information candidates included in the addedinter-prediction information candidate list is smaller than thepreviously designated number of inter-prediction information candidatesand additionally adding the derived inter-prediction informationcandidates to the added inter-prediction information candidate list; acandidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the previouslydesignated number of inter-prediction information candidates when thenumber of inter-prediction information candidates included in theadditionally added inter-prediction information candidate list issmaller than the previously designated number of inter-predictioninformation candidates and additionally adding the derivedinter-prediction information candidates to the additionally addedinter-prediction information candidate list; and a motion-compensatedprediction step of selecting one inter-prediction information candidatefrom the inter-prediction information candidates and performinginter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

An optional combination of the constituent components described aboveand an embodiment obtained by exchanging expressions of the presentinvention among methods, devices, systems, recording media, computerprograms, and the like are also effective as aspects of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a movingpicture coding device that executes a motion vector prediction methodaccording to an embodiment;

FIG. 2 is a block diagram illustrating a configuration of a movingpicture decoding device that executes a motion vector prediction methodaccording to an embodiment;

FIG. 3 is a diagram for describing a tree block and a coding block;

FIGS. 4A to 4H are diagrams for describing a partition mode of aprediction block;

FIG. 5 is a diagram for describing a prediction block of a spatial mergecandidate in a merge mode;

FIG. 6 is a diagram for describing a prediction block of a spatial mergecandidate in a merge mode;

FIG. 7 is a diagram for describing a prediction block of a spatial mergecandidate in a merge mode;

FIG. 8 is a diagram for describing a prediction block of a spatial mergecandidate in a merge mode;

FIG. 9 is a diagram for describing a prediction block of a temporalmerge candidate in a merge mode;

FIG. 10 is a diagram for describing the syntax of a bitstream inrespective prediction blocks in a merge mode;

FIG. 11 is a diagram for describing an example of an entropy symbol of asyntax element of a merge index;

FIG. 12 is a block diagram illustrating a detailed configuration of aninter-prediction information deriving unit of a moving picture codingdevice illustrated in FIG. 1 according to a first practical example;

FIG. 13 is a block diagram illustrating a detailed configuration of aninter-prediction information deriving unit of a moving picture decodingdevice illustrated in FIG. 2 according to a first practical example;

FIGS. 14A to 14H are diagrams for describing a prediction blockneighboring to a processing target prediction block in a merge mode;

FIG. 15 is a flowchart for describing the flow of a process of derivingmerge candidates of a merge mode and a process of constructing a mergecandidate list according to the first practical example;

FIG. 16 is a flowchart for describing the flow of a process of derivingspatial merge candidates of a merge mode;

FIGS. 17A to 17H are diagrams for describing a neighboring blockreferred to in a process of deriving a reference index of a temporalmerge candidate;

FIG. 18 is a flowchart for describing the flow of a process of derivingreference indice of temporal merge candidates of a merge mode;

FIG. 19 is a flowchart for describing the flow of a process of derivingtemporal merge candidates of a merge mode;

FIG. 20 is a flowchart for describing the flow of a process of derivingpictures of different time of a merge mode;

FIG. 21 is a flowchart for describing the flow of a process of derivingprediction blocks of pictures of different time of a merge mode;

FIG. 22 is a flowchart for describing the flow of a process of derivingtemporal merge candidates of a merge mode;

FIG. 23 is a flowchart for describing the flow of a process of derivingtemporal merge candidates of a merge mode;

FIG. 24 is a flowchart for describing the flow of a motion vectorscaling process;

FIG. 25 is a flowchart for describing the flow of a motion vectorscaling process;

FIG. 26 is a flowchart for describing the flow of a process of derivingadditional merge candidates of a merge mode;

FIG. 27 is a flowchart for describing the flow of a merge candidatelimiting process;

FIG. 28 is a block diagram illustrating a detailed configuration of aninter-prediction information deriving unit of a moving picture codingdevice illustrated in FIG. 2 according to second to seventh practicalexamples;

FIG. 29 is a block diagram illustrating a detailed configuration of aninter-prediction information deriving unit of a moving picture decodingdevice illustrated in FIG. 2 according to the second to seventhpractical examples;

FIG. 30 is a flowchart for describing the flow of a process of derivingmerge candidates of a merge mode and a process of constructing a mergecandidate list according to the second to seventh practical examples;

FIG. 31 is a flowchart for describing the flow of a process ofsupplementing valid merge candidates of a merge mode according to thesecond practical example;

FIG. 32 is a flowchart for describing the flow of a process ofsupplementing valid merge candidates of a merge mode according to thethird practical example;

FIG. 33 is a flowchart for describing the flow of a process ofsupplementing valid merge candidates of a merge mode according to thefourth practical example;

FIG. 34 is a flowchart for describing the flow of a process of derivingadditional merge candidates of a merge mode and a process ofsupplementing valid merge candidates according to the fifth practicalexample;

FIG. 35 is a flowchart for describing the flow of a process of makinginitialized inter-prediction information of a merge mode valid as amerge candidate according to the sixth and seventh practical examples;

FIG. 36 is a diagram for describing a temporal direct mode of theconventional MPEG-4 AVC/H.264 standard;

FIG. 37 is a flowchart for describing the flow of the process of aninter-prediction information selecting unit of an inter-predictioninformation deriving unit of a moving picture coding device; and

FIG. 38 is a flowchart for describing the flow of the process of aninter-prediction information selecting unit of an inter-predictioninformation deriving unit of a moving picture decoding device.

DETAILED DESCRIPTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

The present embodiment relates to a moving picture coding technique, andparticularly, to a moving picture coding technique of partitioning apicture into rectangular blocks having optional sizes and shapes andperforming motion compensation between pictures in units of blocks. Inthis technique, a plurality of motion vector predictors is derived froma motion vector of a block neighboring to a coding target block or ablock of a coded picture in order to improve coding efficiency, and avector difference between a motion vector of the coding target block anda selected motion vector predictor is derived and coded to reduce thecoding amount. Alternatively, coding information of the coding targetblock is derived using coding information of a block neighboring to thecoding target block or a block of a coded picture to thereby reduce acoding amount. Moreover, in the case of decoding moving pictures, aplurality of motion vector predictors is derived from a motion vector ofa block neighboring to a decoding target block or a block of a decodedpicture, and a motion vector of the decoding target block is derived anddecoded from a vector difference decoded from a bitstream and a selectedmotion vector predictor. Alternatively, coding information of thedecoding target block is derived using coding information of a blockneighboring to the decoding target block or a block of a decodedpicture.

First, techniques and terms used in the present embodiment are defined.

(Tree Block and Coding Block)

In embodiments, one or a plurality of slices obtained by partitioning apicture is a basic unit of coding, and a slice type which is informationindicating the type of slice is set to each slice. As illustrated inFIG. 3, a slice is evenly partitioned in respective square units havingthe same optional size. This unit square is defined as a tree block andis used as a basic unit of address management for specifying acoding/decoding target block in a slice (a coding target block in codingprocesses and a decoding target block in decoding processes; the same istrue for the following description unless otherwise set forth below). Atree block excluding monochrome components includes one luminance signaland two chroma signals. The size of a tree block can be freely set tothe power of 2 according to a picture size or the texture in a picture.A tree block can be partitioned into blocks having a small block size byhierarchically partitioning the luminance signal and chroma signals inthe tree block into four parts (two parts in vertical and horizontaldirections) as necessary according to the texture in the picture so thata coding process can be optimized. This block is defined as a codingblock and is a basic unit of coding and decoding processes. A codingblock excluding monochrome components includes one luminance signal andtwo chroma signals. A largest size of a coding block is the same as thesize of a tree block. A coding block having the smallest size of thecoding block is referred to as a smallest coding block and can be freelyset to the power of 2.

In FIG. 3, a coding block A is one coding block obtained withoutpartitioning a tree block. A coding block B is a coding block obtainedby partitioning a tree block into four parts. A coding block C is acoding block obtained by partitioning into four parts the block obtainedby partitioning the tree block into four parts. A coding block D is acoding block obtained by partitioning twice into four parts the blockobtained by partitioning the tree block into four parts and is a codingblock having the smallest size.

(Prediction Mode)

Intra-prediction (MODE_INTRA) where prediction is performed fromneighboring picture signals in a coded/decoded state (used in pictures,prediction blocks, picture signals, and the like obtained by decodingcoded signals in the coding process and decoded pictures, predictionblocks, picture signals, and the like in the decoding process; the sameis true for the following description unless otherwise set forth below)in a coding/decoding target picture and inter-prediction (MODE_INTER)where prediction is performed from picture signals of coded/decodedpictures are switched in respective coding blocks. A mode foridentifying the intra-prediction (MODE_INTRA) and the inter-prediction(MODE_INTER) is defined as a prediction mode (PredMode). The predictionmode (PredMode) has a value of intra-prediction (MODE_INTRA) orinter-prediction (MODE_INTER) and can be selected and coded.

(Partition Mode, Prediction Block, and Prediction Unit)

When a picture is partitioned into blocks to perform intra-prediction(MODE_INTRA) and inter-prediction (MODE_INTER), a coding block ispartitioned as necessary to perform prediction in order to furtherreduce the units of switching intra-prediction and inter-prediction. Amode for identifying a method of partitioning the luminance signal andchroma signals of a coding block is defined as a partition mode(PartMode). Further, the partitioned block is defined as a predictionblock. As illustrated in FIGS. 4A to 4H, eight partition modes(PartMode) are defined depending on a method of partitioning theluminance signal of a coding block.

A partition mode (PartMode) in which the luminance signal of a codingblock illustrated in FIG. 4A is not partitioned but is regarded as oneprediction block is defined as 2N×2N partition (PART 2N×2N). Partitionmodes (PartMode) in which the luminance signals of coding blocksillustrated in FIGS. 4B, 4C, and 4D are partitioned into two predictionblocks arranged in the vertical direction are defined as 2N×N partition(PART 2N×N), 2N×nU partition (PART 2N×nU), and 2N×nD partition (PART2N×nD), respectively. Here, 2N×N partition (PART 2N×N) is a partitionmode in which the luminance signal is partitioned in the ratio of 1:1 inthe vertical direction, 2N×nU partition (PART 2N×nU) is a partition modein which the luminance signal is partitioned in the ratio of 1:3 in thevertical direction, and 2N×nD partition (PART 2N×nD) is a partition modein which the luminance signal is partitioned in the ratio of 3:1 in thevertical direction. Partition modes (PartMode) in which the luminancesignals of coding blocks illustrated in FIGS. 4E, 4F, and 4G arepartitioned into two prediction blocks arranged in the horizontaldirection are defined as N×2N partition (PART_N×2N), nL×2N partition(PART_nL×2N), and nR×2N partition (PART_nR×2N), respectively. Here, N×2Npartition (PART_N×2N) is a partition mode in which the luminance signalis partitioned in the ratio of 1:1 in the horizontal direction, nL×2Npartition (PART_nL×2N) is a partition mode in which the luminance signalis partitioned in the ratio of 1:3 in the horizontal direction, andnR×2N partition (PART_nR×2N) is a partition mode in which the luminancesignal is partitioned in the ratio of 3:1 in the horizontal direction. Apartition mode (PartMode) in which the luminance signal of a codingblock illustrated in FIG. 4H is partitioned into four parts in thevertical and horizontal directions to obtain four prediction blocks isdefined as N×N partition (PART_N×N).

The chroma signal is partitioned in the same vertical and horizontalpartition ratios as the luminance signal in respective partition modes(PartMode).

In order to specify each prediction block in a coding block, a numberstarting from 0 is allocated to prediction blocks present in the codingblock in the coding order. This number is defined as a partition indexPartIdx. The number described in each prediction block of the codingblock illustrated in FIGS. 4A to 4H indicates a partition index PartIdxof the prediction block. In the 2N×N partition (PART 2N×N), 2N×nUpartition (PART 2N×nU), and 2N×nD partition (PART 2N×nD) illustrated inFIGS. 4B, 4C, and 4D, the partition indice PartIdx of the upperprediction blocks are set to 0 and the partition indice PartIdx of thelower prediction blocks are set to 1. In the N×2N partition (PART_N×2N),nL×2N partition (PART_nL×2N), and nR×2N partition (PART_nR×2N)illustrated in FIGS. 4E, 4F, and 4G, the partition indice PartIdx of theleft prediction blocks are set to 0 and the partition indice PartIdx ofthe right prediction blocks are set to 1. In the N×N partition(PART_N×N) illustrated in FIG. 4H, the partition index PartIdx of thetop-left prediction block is set to 0, the partition index PartIdx ofthe top-right prediction block is set to 1, the partition index PartIdxof the bottom-left prediction block is set to 2, and the partition indexPartIdx of the bottom-right prediction block is set to 3.

When the prediction mode (PredMode) is inter-prediction (MODE_INTER),2N×2N partition (PART_2N×2N), 2N×N partition (PART_2N×N), 2N×nUpartition (PART_2N×nU), 2N×nD partition (PART_2N×nD), N×2N partition((PART_N×2N), nL×2N partition (PART_nL×2N), and nR×2N partition(PART_nR×2N) are defined as the partition modes (PartMode). As for thecoding block D only which is the smallest coding block, N×N partition(PART_N×N) may be defined as the partition mode (PartMode) in additionto 2N×2N partition (PART_2N×2N), 2N×N partition (PART_2N×N), 2N×nUpartition (PART_2N×nU), 2N×nD partition (PART_2N×nD), N×2N partition((PART_N×2N), nL×2N partition (PART_nL×2N), and nR×2N partition(PART_nR×2N). However, in the present embodiment, N×N partition(PART_N×N) is not defined as the partition mode (PartMode).

When the prediction mode (PredMode) is intra-prediction (MODE_INTRA),2N×2N partition (PART_2N×2N) only is defined for coding blocks otherthan the coding block D which is the smallest coding block as thepartition mode (PartMode), and N×N partition (PART_N×N) is defined forthe coding block D only which is the smallest coding block as thepartition mode (PartMode) in addition to 2N×2N partition (PART_2N×2N).The reason why N×N partition (PART_N×N) is not defined for coding blocksother than the smallest coding block is because it is possible topartition a coding block other than the smallest coding block into fourparts to express smaller coding blocks.

(Positions of Tree Block, Coding Block, Prediction Block, TransformBlock)

The positions of blocks including a tree block, a coding block, aprediction block, and a transform block of the present embodiment arerepresented such that the position of a pixel of a top-left luminancesignal of a screen of the luminance signal is set as the origin (0, 0),and the position of a pixel of the top-left luminance signal included inthe region of each block is represented by a two-dimensional coordinate(x, y). The direction of the coordinate axis is defined such that therightward direction of the horizontal direction and the downwarddirection of the vertical direction are the positive directions, and theunit is one pixel of the luminance signal. When the chroma format is4:2:0 or 4:2:2 where the picture size (the number of pixels) isdifferent from luminance signal to chroma signal as well as when thechroma format is 4:4:4 where the picture size (the number of pixels) isthe same for the luminance signal and the chroma signal, the position ofeach block of the chroma signal is represented by the coordinate of apixel of a luminance signal included in the region of the block, and theunit is one pixel of the luminance signal. By doing so, it is possibleto specify the position of each block of the chroma signal and toclearly understand the positional relation between the block of theluminance signal and the block of the chroma signal just by comparingthe coordinate values.

(Inter-Prediction Mode and Reference List)

In the embodiment of the present invention, a plurality of decodedpictures can be used as reference pictures in inter-prediction in whichprediction is performed from picture signals of coded/decoded pictures.In order to specify reference pictures selected from a plurality ofreference pictures, a reference index is allocated to each predictionblock. In B slices, it is possible to select optional two referencepictures for each prediction block and to perform inter-prediction, andexamples of the inter-prediction mode include L0 prediction (Pred_L0),L1 prediction (Pred_L1), and bi-prediction (Pred_BI). Reference picturesare managed by L0 (Reference list 0) and L1 (Reference list 1) of a liststructure, and a reference picture can be specified by designating thereference index of L0 or L1. L0 prediction (Pred_L0) is inter-predictionwhich refers to reference pictures managed by L0, L1 prediction(Pred_L1) is inter-prediction which refers to reference pictures managedby L1, and bi-prediction (Pred_BI) is inter-prediction in which both L0prediction and L1 prediction are performed and which refers to referencepictures managed by L0 and L1, respectively. L0 prediction only can beused in inter-prediction of P slices, and L0 prediction, L1 prediction,and bi-prediction (Pred_BI) in which L0 prediction and L1 prediction areaveraged or weight-added can be used in inter-prediction of B slices. Inthe following processes, it is assumed that integers and variables towhich a character LX is appended to the output are processed for each ofL0 and L1.

(Merge Mode and Merge Candidate)

A merge mode is a mode in which rather than inter-prediction informationsuch as a prediction mode, a reference index, or a motion vector of acoding/decoding target prediction block is coded and decoded,inter-prediction is performed by deriving inter-prediction informationof a coding/decoding target prediction block from inter-predictioninformation of prediction blocks neighboring to the coding/decodingtarget prediction block in the same picture as the coding/decodingtarget prediction block or a prediction block present at the sameposition as or near (at the position neighboring) a coding/decodingtarget prediction block of a coded/decoded picture at a differenttemporal position from the coding/decoding target prediction block. Aprediction block neighboring to the coding/decoding target predictionblock in the same picture as the coding/decoding target prediction blockand inter-prediction information of the prediction block are referred toas spatial merge candidates, and a prediction block present at the sameposition as or near (the position neighboring) the coding/decodingtarget prediction block of a coded/decoded picture at a temporallydifferent position from the coding/decoding target prediction block andinter-prediction information derived from the inter-predictioninformation of the prediction block are referred to as temporal mergecandidates. The respective merge candidates are added to a mergecandidate list and a merge candidate used for inter-prediction isspecified by a merge index.

(Neighboring Prediction Block)

FIGS. 5, 6, 7, and 8 are diagrams for describing prediction blocksneighboring to a coding/decoding target prediction block in the samepicture as the coding/decoding target prediction block that is referredto when deriving spatial merge candidates and reference indice oftemporal merge candidates. FIG. 9 is a diagram for describingcoded/decoded prediction blocks present at the same position as or neara coding/decoding target prediction block of a coded/decoded picture ata temporally different position from the coding/decoding targetprediction block that is referred to when deriving temporal mergecandidates. Prediction blocks neighboring in a spatial direction of acoding/decoding target prediction block and prediction blocks at thesame position of different time will be described using FIGS. 5, 6, 7,8, and 9.

As illustrated in FIG. 5, a prediction block A neighboring to a leftside of a coding/decoding target prediction block in the same picture asthe coding/decoding target prediction block, a prediction block Bneighboring to an upper side of the coding/decoding target predictionblock, a prediction block C neighboring to a top-right corner of thecoding/decoding target prediction block, a prediction block Dneighboring to a bottom-left corner of the coding/decoding targetprediction block, and a prediction block E neighboring to a top-leftcorner of the coding/decoding target prediction block are defined asprediction blocks neighboring in the spatial direction.

As illustrated in FIG. 6, when a plurality of prediction blocksneighboring to the left side of the coding/decoding target predictionblock is present and has a smaller size than the coding/decoding targetprediction block, only the lowermost prediction block A10 among theprediction blocks neighboring to the left side will be referred to asthe prediction block A neighboring to the left side in the presentembodiment.

Similarly, when a plurality of prediction blocks neighboring to theupper side of the coding/decoding target prediction block is present andhas a smaller size than the coding/decoding target prediction block,only the rightmost prediction block B10 among the prediction blocksneighboring to the left side will be referred to as the prediction blockB neighboring to the upper side in the present embodiment.

As illustrated in FIG. 7, even when the size of the prediction block Fneighboring to the left side of the coding/decoding target predictionblock is larger than the coding/decoding target prediction block,according to the conditions, the prediction block F is the predictionblock A if the prediction block F neighboring to the left side neighborsto the left side of the coding/decoding target prediction block, theprediction block D if the prediction block F neighbors to thebottom-left corner of the coding/decoding target prediction block, andthe prediction block E if the prediction block F neighbors to thetop-left corner of the coding/decoding target prediction block. In theexample of FIG. 7, the prediction block A, the prediction block D, andthe prediction block E are the same prediction blocks.

As illustrated in FIG. 8, even when the size of the prediction block Gneighboring to the upper side of the coding/decoding target predictionblock is larger than the coding/decoding target prediction block,according to the conditions, the prediction block G is the predictionblock B if the prediction block G neighboring to the upper sideneighbors to the upper side of the coding/decoding target predictionblock, the prediction block C if the prediction block G neighbors to thetop-right corner of the coding/decoding target prediction block, and theprediction block E if the prediction block G neighbors to the top-leftcorner of the coding/decoding target prediction block. In the example ofFIG. 8, the prediction block B, the prediction block C, and theprediction block E are the same prediction blocks.

As illustrated in FIG. 9, in coded/decoded pictures at temporallydifferent positions from the coding/decoding target prediction block,coded/decoded prediction blocks T0 and T1 present at the same positionas or near the coding/decoding target prediction block are defined asprediction blocks at the same position of different time.

(POC)

A POC is a variable associated with a picture to be coded and a valuethat is incremented by 1 in the picture outputting/displaying order isset as the POC. Based on the POC value, it is possible to determinewhether two pictures are the same picture, determine an anteroposteriorrelation between pictures in the outputting/displaying order, and derivea picture-to-picture distance. For example, when two pictures have thesame POC value, it can be determined that both pictures are the samepicture. When two pictures have different POC values, it can bedetermined that a picture having the smaller POC value is a picture thatis output and displayed earlier, and a difference between POCs of twopictures indicates a picture-to-picture distance in a time axisdirection.

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings. FIG. 1 is a block diagram illustrating aconfiguration of a moving picture coding device according to anembodiment of the present invention. The moving picture coding device ofthe embodiment includes a picture memory 101, a header informationsetting unit 117, a motion vector detector 102, a motion vectordifference deriving unit 103, an inter-prediction information derivingunit 104, a motion-compensated prediction unit 105, an intra-predictionunit 106, a prediction method determining unit 107, a residual signalconstructing unit 108, an orthogonal transformation and quantizationunit 109, a first bitstream constructing unit 118, a second bitstreamconstructing unit 110, a third bitstream constructing unit 111, amultiplexer 112, a dequantization and inverse-orthogonal transformationunit 113, a decoded picture signal superimposing unit 114, a codinginformation storage memory 115, and a decoded picture memory 116.

The header information setting unit 117 sets information in sequence,picture, and slide units. The set information in sequence, picture, andslice units is supplied to the inter-prediction information derivingunit 104 and the first bitstream constructing unit 118 and is alsosupplied to all blocks although not illustrated in the drawing. Theheader information setting unit 117 also sets a largest number of mergecandidates maxNumMergeCand described later.

The picture memory 101 temporarily stores picture signals of codingtarget pictures supplied in the order of the time at which the picturesare captured and displayed. The picture memory 101 supplies the storedpicture signals of coding target pictures to the motion vector detector102, the prediction method determining unit 107, and the residual signalconstructing unit 108 in units of predetermined pixel blocks. In thiscase, the picture signals of the pictures stored in thecapturing/displaying order are rearranged in the coding order and areoutput from the picture memory 101 in units of pixel blocks.

The motion vector detector 102 detects a motion vector of eachprediction block size and each prediction mode in respective predictionblocks by performing block matching between the picture signals suppliedfrom the picture memory 101 and the reference pictures supplied from thedecoded picture memory 116 and supplies the detected motion vector tothe motion-compensated prediction unit 105, the motion vector differencederiving unit 103, and the prediction method determining unit 107.

The motion vector difference deriving unit 103 derives a plurality ofmotion vector predictor candidates using coding information of codedpicture signals stored in the coding information storage memory 115 toadd the same in a motion vector predictor list, selects an optimalmotion vector predictor among the plurality of motion vector predictorcandidates added to the motion vector predictor list, derives a motionvector difference from the motion vector predictor and the motion vectordetected by the motion vector detector 102, and supplies the derivedmotion vector difference to the prediction method determining unit 107.Further, the motion vector difference deriving unit 103 supplies amotion vector predictor index for specifying the motion vector predictorselected from the motion vector predictor candidates added to the motionvector predictor list to the prediction method determining unit 107.

The inter-prediction information deriving unit 104 derives mergecandidates in a merge mode. The inter-prediction information derivingunit 104 derives a plurality of merge candidates using the codinginformation of the coded prediction blocks stored in the codinginformation storage memory 115 to add the same to a merge candidate listdescribed later, selects an optimal merge candidate among the pluralityof merge candidates added to the merge candidate list, suppliesinter-prediction information such as flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] indicating whether or not to use L0 prediction and L1prediction of each prediction block of the selected merge candidate,reference indice refIdxL0[xP][yP] and refIdxL1[xP][yP], and motionvectors mvL0[xP][yP] and mvL1[xP][yP] to the motion-compensatedprediction unit 105, and supplies a merge index for specifying theselected merge candidate to the prediction method determining unit 107.Here, xP and yP are indice indicating the position of the top-left pixelof a prediction block in the picture. Detailed configuration andoperations of the inter-prediction information deriving unit 104 will bedescribed later.

The motion-compensated prediction unit 105 constructs a predictionpicture signal by performing inter-prediction (motion-compensatedprediction) from reference pictures using the motion vector detected bythe motion vector detector 102 and the inter-prediction informationderiving unit 104 and supplies the prediction picture signal to theprediction method determining unit 107. In L0 prediction and L1prediction, prediction is performed in one direction. In the case ofbi-prediction (Pred_BI), prediction is performed in two directions toobtain inter-prediction signals in L0 and L1 prediction modes, which areadaptively multiplied by a weighting factor and are superimposed byadding an offset value to thereby construct a final prediction picturesignal.

The intra-prediction unit 106 performs intra-prediction in respectiveintra-prediction modes. The intra-prediction unit 106 constructsprediction picture signals by performing intra-prediction from thedecoded picture signals stored in the decoded picture memory 116,selects an optimal intra-prediction mode among a plurality ofintra-prediction modes, and supplies a prediction picture signalcorresponding to the selected intra-prediction mode to the predictionmethod determining unit 107.

The prediction method determining unit 107 evaluates coding information,a coding amount of a residual signal, and a distortion amount between aprediction picture signal and a picture signal of each prediction methodto thereby determine a partition mode PartMode and a prediction modePredMode for identifying the prediction mode is inter-prediction(PRED_INTER) or intra-prediction (PRED_INTRA) for each optimal codingblock among a plurality of prediction methods, determine whether theinter-prediction (PRED_INTER) is a merge mode in respective predictionblocks, determine a merge index when the inter-prediction is the mergemode, and determine an inter-prediction mode, a motion vector predictorindex, L0 and L1 reference indice, a motion vector difference, and thelike when the inter-prediction is not the merge mode, and suppliescoding information corresponding to the determination to the secondbitstream constructing unit 110.

Further, the prediction method determining unit 107 stores codinginformation including information indicating the determined predictionmethod and a motion vector and the like corresponding to the determinedprediction method in the coding information storage memory 115. Thecoding information stored herein includes a prediction mode PredMode ofeach coding block, a partition mode PartMode, flags predFlagL0[xP][yP]and predFlagL1[xP][yP] indicating whether or not to use L0 predictionand L1 prediction of each prediction block, L0 and L1 reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP], and L0 and L1 motion vectorsmvL0[xP][yP] and mvL1[xP][yP]. Here, xP and yP are indice indicating theposition of the top-left pixel of a prediction block in the picture.When the prediction mode PredMode is intra-prediction (MODE_INTRA), boththe flag predFlagL0[xP][yP] indicating whether or not to use L0prediction and the flag predFlagL1[xP][yP] indicating whether or not touse L1 prediction are 0. On the other hand, when the prediction modePredMode is inter-prediction (MODE_INTER) and the inter-prediction modeis L0 prediction (Pred_L0), the flag predFlagL0[xP][yP] indicatingwhether or not to use L0 prediction is 1 and the flag predFlagL1[xP][yP]indicating whether or not to use L1 prediction is 0. When theinter-prediction mode is L1 prediction (Pred_L1), the flagpredFlagL0[xP][yP] indicating whether or not to use L0 prediction is 0and the flag predFlagL1[xP][yP] indicating whether or not to use L1prediction is 1. When the inter-prediction mode is bi-prediction(Pred_BI), both the flag predFlagL0[xP][yP] indicating whether or not touse L0 prediction and the flag predFlagL1[xP][yP] indicating whether ornot to use L1 prediction are 1. The prediction method determining unit107 supplies the prediction picture signal corresponding to thedetermined prediction mode to the residual signal constructing unit 108and the decoded picture signal superimposing unit 114.

The residual signal constructing unit 108 constructs a residual signalby performing subtraction between a picture signal to be coded and theprediction picture signal and supplies the same to the orthogonaltransformation and quantization unit 109.

The orthogonal transformation and quantization unit 109 performsorthogonal transformation and quantization on the residual signalaccording to a quantization parameter to construct an orthogonallytransformed and quantized residual signal and supplies the same to thethird bitstream constructing unit 111 and the dequantization andinverse-orthogonal transformation unit 113. Further, the orthogonaltransformation and quantization unit 109 stores the quantizationparameter in the coding information storage memory 115.

The first bitstream constructing unit 118 codes the information insequence, picture, and slice units set by the header information settingunit 117 to construct a first bitstream and supplies the same to themultiplexer 112. The first bitstream constructing unit 118 also codes alargest number of merge candidates maxNumMergeCand described later.

The second bitstream constructing unit 110 codes the coding informationcorresponding to the prediction method determined by the predictionmethod determining unit 107 for each coding block and each predictionblock. Specifically, the second bitstream constructing unit 110 codescoding information according to a predetermined syntax rule describedlater to construct a second bitstream and supplies the same to themultiplexer 112, the coding information including information foridentifying whether each coding block is a skip mode, a prediction modePredMode for identifying inter-prediction (PRED_INTER) andintra-prediction (PRED_INTRA), a partition mode PartMode, anintra-prediction mode when the prediction mode is intra-prediction(PRED_INTRA), a flag for identifying whether the inter-prediction(PRED_INTER) is a merge mode, a merge index when the inter-predictionmode is a merge mode, and an inter-prediction mode, a motion vectorpredictor index, and information on the motion vector difference whenthe inter-prediction mode is not a merge mode. In the presentembodiment, when the coding block is a skip mode (the syntax elementskip_flag[x0][y0] is 1), the value of the prediction mode PredMode of aprediction block is inter-prediction (MODE_INTER), a merge mode(merge_flag[x0][y0] is 1), and the partition mode (PartMode) is 2N×2Npartition (PART_2N×2N).

The third bitstream constructing unit 111 performs entropy coding on theorthogonally transformed and quantized residual signal according to apredetermined syntax rule to construct a third bitstream and suppliesthe same to the multiplexer 112. The multiplexer 112 multiplies thefirst, second, and third bitstreams according to the predeterminedsyntax rule and outputs the multiplexed bitstream.

The dequantization and inverse-orthogonal transformation unit 113performs dequantization and inverse-orthogonal transformation on theorthogonally transformed and quantized residual signal supplied from theorthogonal transformation and quantization unit 109 to construct theresidual signal and supplies the same to the decoded picture signalsuperimposing unit 114. The decoded picture signal superimposing unit114 superimposes the prediction picture signal corresponding to thedetermination of the prediction method determining unit 107 and theresidual signal dequantized and inverse-orthogonally transformed by thedequantization and inverse-orthogonal transformation unit 113 toconstruct a decoded picture and stores the same in the decoded picturememory 116. A filtering process of reducing distortion such as blockdistortion resulting from coding may be applied to the decoded pictureand the resultant picture may be stored in the decoded picture memory116.

FIG. 2 is a block diagram illustrating a configuration of a movingpicture decoding device according to an embodiment of the presentinvention, corresponding to the moving picture coding device of FIG. 1.The moving picture decoding device of the embodiment includes ademultiplexer 201, a first bitstream decoder 212, a second bitstreamdecoder 202, a third bitstream decoder 203, a motion vector derivingunit 204, an inter-prediction information deriving unit 205, amotion-compensated prediction unit 206, an intra-prediction unit 207, adequantization and inverse-orthogonal transformation unit 208, a decodedpicture signal superimposing unit 209, a coding information storagememory 210, and a decoded picture memory 211.

Since the decoding process of the moving picture decoding deviceillustrated in FIG. 2 corresponds to the decoding process performed inthe moving picture coding device illustrated in FIG. 1, the respectivecomponents of the motion-compensated prediction unit 206, thedequantization and inverse-orthogonal transformation unit 208, thedecoded picture signal superimposing unit 209, the coding informationstorage memory 210, and the decoded picture memory 211 illustrated inFIG. 2 have the functions corresponding to the respective components ofthe motion-compensated prediction unit 105, the dequantization andinverse-orthogonal transformation unit 113, the decoded picture signalsuperimposing unit 114, the coding information storage memory 115, andthe decoded picture memory 116 of the moving picture coding deviceillustrated in FIG. 1.

The bitstream supplied to the demultiplexer 201 is demultiplexedaccording to a predetermined syntax rule and the demultiplexed bitstreamis supplied to the first, second, and third bitstream decoders 212, 202,and 203.

The first bitstream decoder 212 decodes the supplied bitstream to obtaininformation in sequence, picture, and slice units. The obtainedinformation in sequence, picture, and slice units is supplied to allblocks although not illustrated in the drawing. The first bitstreamdecoder 212 also decodes a largest number of merge candidatesmaxNumMergeCand described later.

The second bit stream decoder 202 decodes the supplied bitstream toobtain information in coding block units and coding information inprediction block units. Specifically, the second bitstream decoder 202decodes coding information according to the predetermined syntax rule toobtain coding information, stores the coding information such as thedecoded prediction mode PredMode and the decoded partition mode PartModein the coding information storage memory 210, and supplies the same tothe motion vector deriving unit 204, the inter-prediction informationderiving unit 205, or the intra-prediction unit 207, the codinginformation including information for identifying whether each codingblock is a skip mode, a prediction mode PredMode for identifying whetherthe prediction mode is inter-prediction (PRED_INTER) or intra-prediction(PRED_INTRA), a partition mode PartMode, a flag for identifying whetherinter-prediction (PRED_INTER) is a merge mode, a merge index when theinter-prediction is a merge mode, and an inter-prediction mode, a motionvector predictor index, and a motion vector difference when theinter-prediction is not a merge mode. In the present embodiment, whenthe coding block is a skip mode (the syntax element skip_flag[x0][y0] is1), the value of the prediction mode PredMode of a prediction block isinter-prediction (MODE_INTER), a merge mode (merge_flag[x0][y0] is 1),and the partition mode (PartMode) is 2N×2N partition (PART_2N×2N).

The third bitstream decoder 203 decodes the supplied bitstream to derivean orthogonally transformed and quantized residual signal and suppliesthe orthogonally transformed and quantized residual signal to thedequantization and inverse-orthogonal transformation unit 208.

When the prediction mode PredMode of a decoding target prediction blockis not the inter-prediction (PRED_INTER) or the merge mode, the motionvector deriving unit 204 derives a plurality of motion vector predictorcandidates using the coding information of the decoded picture signalstored in the coding information storage memory 210 to add the same to amotion vector predictor list described later, and selects a motionvector predictor corresponding to the motion vector predictor indexdecoded and supplied by the second bit stream decoder 202 among theplurality of motion vector predictor candidates added in the motionvector predictor list, derives a motion vector from the selected motionvector predictor and the vector difference decoded by the secondbitstream decoder 202, supplies the same to the motion-compensatedprediction unit 206 together with other items of coding information, andstores the same in the coding information storage memory 210. The codinginformation of the prediction block supplied and stored herein includesflags predFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whether ornot to use L0 prediction and L1 prediction, L0 and L1 reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP], and L0 and L1 motion vectorsmvL0[xP][yP] and mvL1[xP][yP]. Here, xP and yP are indice indicating theposition of the top-left pixel of a prediction block in the picture.When the prediction mode PredMode is inter-prediction (MODE_INTER) andthe inter-prediction mode is L0 prediction (Pred_L0), a flag predFlagL0indicating whether or not to use L0 prediction is 1 and a flagpredFlagL1 indicating whether or not to use L1 prediction is 0. When theinter-prediction mode is L1 prediction (Pred_L1), a flag predFlagL0indicating whether or not to use L0 prediction is 0 and a flagpredFlagL1 indicating whether or not to use L1 prediction is 1. When theinter-prediction mode is bi-prediction (Pred_BI), both the flagpredFlagL0 indicating whether or not to use L0 prediction and the flagpredFlagL1 indicating whether or not to use L1 prediction are 1.

The inter-prediction information deriving unit 205 derives mergecandidates when the prediction mode PredMode of a decoding targetprediction block is inter-prediction (PRED_INTER) and a merge mode. Theinter-prediction information deriving unit 205 derives a plurality ofmerge candidates using the decoded coding information of the predictionblock stored in the coding information storage memory 115 to add thesame to a merge candidate list described later, selects a mergecandidate corresponding to the merge index decoded and supplied by thesecond bitstream decoder 202 among the plurality of merge candidatesadded to the merge candidate list, supplies inter-prediction informationincluding flags predFlagL0[xP][yP] and predFlagL1[xP][yP] indicatingwhether or not to use L0 prediction and L1 prediction of the selectedmerge candidate, L0 and L1 reference indice refIdxL0[xP][yP] andrefIdxL1[xP][yP], and L0 and L1 motion vectors mvL0[xP][yP] andmvL1[xP][yP] to the motion-compensated prediction unit 206, and storesthe same in the coding information storage memory 210. Here, xP and yPare indice indicating the position of the top-left pixel of a predictionblock in the picture. Detailed configuration and operations of theinter-prediction information deriving unit 205 will be described later.

The motion-compensated prediction unit 206 constructs a predictionpicture signal by performing inter-prediction (motion-compensatedprediction) from the reference pictures stored in the decoded picturememory 211 using the inter-prediction information derived by the motionvector deriving unit 204 or the inter-prediction information derivingunit 205 and supplies the prediction picture signal to the decodedpicture signal superimposing unit 209. In the case of bi-prediction(Pred_BI), motion-compensated prediction is performed in two modes of L0prediction and L1 prediction to obtain motion-compensated predictionpicture signals which are adaptively multiplied by a weighting factorand are superimposed to thereby construct a final prediction picturesignal.

The intra-prediction unit 207 performs intra-prediction when theprediction mode PredMode of the decoding target prediction block isintra-prediction (PRED_INTRA). The coding information decoded by thesecond bitstream decoder 202 includes an intra-prediction mode, and theintra-prediction unit 207 constructs a prediction picture signal byperforming intra-prediction from the decoded picture signal stored inthe decoded picture memory 211 according to the intra-prediction modeand supplies the prediction picture signal to the decoded picture signalsuperimposing unit 209. Both the flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] indicating whether or not to use L0 prediction and L1prediction are set to 0 and are stored in the coding information storagememory 210. Here, xP and yP are indice indicating the position of thetop-left pixel of a prediction block in the picture.

The dequantization and inverse-orthogonal transformation unit 208performs dequantization and inverse-orthogonal transformation on theorthogonally transformed and quantized residual signal decoded by thesecond bitstream decoder 202 to obtain a dequantizated andinverse-orthogonally transformed residual signal.

The decoded picture signal superimposing unit 209 superimposes theprediction picture signal inter-predicted by the motion-compensatedprediction unit 206 or the prediction picture signal intra-predicted bythe intra-prediction unit 207 on the residual signal dequantizated andinverse-orthogonally transformed by the dequantization andinverse-orthogonal transformation unit 208 to decode a decoded picturesignal and stores the same in the decoded picture memory 211. When thedecoded picture signal is stored in the decoded picture memory 211, afiltering process of reducing a block distortion or the like resultingfrom coding may be performed on the decoded picture and stored in thedecoded picture memory 211.

(Syntax)

Next, a syntax which is a common rule of coding and decoding a movingpicture bitstream which is coded by a moving picture coding deviceemploying a motion vector prediction method according to the presentembodiment and decoded by a decoding device will be described.

In the present embodiment, the header information setting unit 117 setsa largest number of merge candidates maxNumMergeCand added to the mergecandidate list mergeCandList in sequence, picture, or slice units, andsyntax elements are coded by the first bitstream constructing unit 118of the moving picture coding device and are decoded by the firstbitstream decoder 212 of the moving picture decoding device. A valuefrom 0 to 5 can be set to the largest number of merge candidatesmaxNumMergeCand, and mainly, a small value is set to the largest numberof merge candidates maxNumMergeCand when a processing amount of themoving picture coding device is to be reduced. When 0 is set to thelargest number of merge candidates maxNumMergeCand, predeterminedinter-prediction information is used as a merge candidate. In thedescription of the present embodiment, the largest number of mergecandidates maxNumMergeCand is set to 5.

FIG. 10 illustrates a syntax rule described in prediction block units.In the present embodiment, when the coding block is a skip mode (thesyntax element skip_flag[x0][y0] is 1), the value of the prediction modePredMode of the prediction block is inter-prediction (MODE_INTER) andthe merge mode (merge_flag[x0][y0] is 1) and the partition mode(PartMode) is 2N×2N partition (PART_2N×2N). When the flagmerge_flag[x0][y0] is 1, it indicates that the prediction mode is amerge mode. When the value of the largest number of merge candidatesmaxNumMergeCand is larger than 1, a syntax element merge_idx[x0][y0] ofan index of a merge list which is the list of merge candidates to bereferred to is provided. When the flag skip_flag[x0][y0] is 1, itindicates that the coding block is a skip mode. When the value of thelargest number of merge candidates maxNumMergeCand is larger than 1, asyntax element merge_idx[x0][y0] of an index of a merge list which is alist of merge candidates to be referred to is provided.

When the value of the prediction mode PredMode of a prediction block isinter-prediction (MODE_INTER), a flag merge_flag[x0][y0] indicatingwhether the prediction block is a merge mode is provided. Here, x0 andy0 are indice indicating the position of a pixel at the top-left cornerof a prediction block in a picture of a luminance signal, and the flagmerge_flag[x0][y0] is a flag indicating whether the prediction blockpositioned at (x0, y0) in the picture is a merge mode.

Subsequently, when the flag merge_flag[x0][y0] is 1, it indicates thatthe prediction block is a merge mode. When the value of the largestnumber of merge candidates maxNumMergeCand is 1, a syntax elementmerge_idx[x0][y0] of an index of a merge list which is a list of mergecandidates to be referred to is provided. Here, x0 and y0 are indiceindicating the position of a pixel at the top-left corner of aprediction block in the picture and an index merge_idx[x0][y0] is amerge index of a prediction block positioned at (x0,y0) in the picture.When a merge index is subjected to entropy-coding/decoding, the smallerthe number of merge candidates, the smaller coding amount and thesmaller processing amount with which the coding/decoding can beperformed. FIG. 11 illustrates an example of an entropy symbol (code) ofthe syntax element merge_idx[x0][y0] of a merge index. When the largestnumber of merge candidates is 2 and the merge indice are 0 and 1, thesymbols of the syntax element merge_idx[x0][y0] of the merge index are‘0’ and ‘1’, respectively. When the largest number of merge candidatesis 3 and the merge indice are 0, 1, and 2, the symbols of the syntaxelement merge_idx[x0][y0] of the merge index are ‘0’, ‘10’, and ‘11’,respectively. When the largest number of merge candidates is 4 and themerge indice are 0, 1, 2, and 3, the symbols of the merge_idx[x0][y0] ofthe merge index are ‘0’, ‘10’, ‘110’, and ‘111’, respectively. When thelargest number of merge candidates is 5 and the merge indice are 0, 1,2, 3, and 4, the symbols of the merge_idx[x0][y0] of the merge index are‘0’, ‘10’, ‘110’, ‘1110’, and ‘1111’, respectively. That is, when thelargest number of merge candidates maxNumMergeCand added to the mergecandidate list mergeCandList is known, a merge index having the smallerlargest number of merge candidates maxNumMergeCand can be representedwith a smaller coding amount. In the present embodiment, as illustratedin FIG. 11, the coding amount of the merge indice is reduced byswitching symbols indicating the values of the merge indice according tothe number of merge candidates. In the present embodiment, a merge indexhaving a value larger than or equal to the value of the largest numberof merge candidates maxNumMergeCand will not be coded or decoded. Whenthe largest number of merge candidates maxNumMergeCand is 1, the mergeindex is not coded/decoded and the merge index is 0. Moreover, thelargest number of merge candidates is 0, the merge index is not requiredsince the predetermined inter-prediction information is used as themerge candidate.

On the other hand, when the flag merge_flag[x0][y0] is 0, it indicatesthat the prediction mode is not a merge mode. When the slice type is theB-slice, a syntax element inter_pred_flag[x0][y0] for identifying aninter-prediction mode is provided, and L0 prediction (Pred_L0), L1prediction (Pred_L1), and bi-prediction (Pred_BI) are identified by thesyntax element. A syntax element ref_idx_l0[x0][y0] andref_idx_l1[x0][y0] of a reference index for identifying a referencepicture and a syntax element mvd_l0[x0][y0][j] and mvd_l1[x0][y0][j] ofa motion vector difference which is a difference between the motionvector predictor and the motion vector of the prediction block obtainedby motion vector detection are provided for the respective lists L0 andL1. Here, x0 and y0 are indices indicating the position of a pixel atthe top-left corner of a prediction block in the picture,ref_idx_l0[x0][y0] and mvd_l0[x0][y0][j] are the L0 reference index andmotion vector difference of the prediction block positioned at (x0, y0)in the picture, respectively, and ref_idx_l1[x0][y0] andmvd_l1[x0][y0][j] are the L1 reference index and motion vectordifference of the prediction block positioned at (x0, y0) in thepicture, respectively. Moreover, j indicates the component of the motionvector difference, j=0 indicates an x-component, and j=1 indicates ay-component. Subsequently, a syntax element mvp_idx_l0 [x0][y0] andmvp_idx_l1 [x0][y0] of an index of a motion vector predictor list whichis a list of motion vector predictor candidates to be referred to isprovided. Here, x0 and y0 are indice indicating the position of a pixelat the top-left corner of a prediction block in the picture, andmvp_idx_l0 [x0][y0] and mvp_idx_l1 [x0][y0] is a L0 and L1 motion vectorpredictor index of the prediction block positioned at (x0, y0) in thepicture. In the present embodiment of the present invention, the valueof the number of these candidates is set to 2.

A inter-prediction information deriving method according to theembodiment is performed by the inter-prediction information derivingunit 104 of the moving picture coding device illustrated in FIG. 1 andthe inter-prediction information deriving unit 205 of the moving picturedecoding device illustrated in FIG. 2.

The inter-prediction information deriving method according to theembodiment will be described with reference to the drawings. A motionvector prediction method is performed in the coding and decoding processin units of prediction blocks that constitute a coding block. When theprediction mode PredMode of a prediction block is inter-prediction(MODE_INTER) and a merge mode including a skip mode, the motion vectorprediction method is performed when deriving a prediction mode, areference index, and a motion vector of a coding target prediction blockusing a prediction mode, a reference index, and a motion vector of acoded prediction block in the case of coding and is performed whenderiving a prediction mode, a reference index, and a motion vector of adecoding target prediction block using a prediction mode, a referenceindex, and a motion vector of a decoded prediction block in the case ofdecoding.

In the merge mode, merge candidates are derived from prediction blocksincluding a prediction block Col (T0 or T1) present at the same positionof different time or near a coding target prediction block describedwith reference to FIG. 9 in addition to the five prediction blocks ofthe prediction block A neighboring to the left side, the predictionblock B neighboring to the upper side, the prediction block Cneighboring to the top-right corner, the prediction block D neighboringto the bottom-left corner, and the prediction block E neighboring to thetop-left corner described with reference to FIGS. 5, 6, 7, and 8. Theinter-prediction information deriving unit 104 of the moving picturecoding device and the inter-prediction information deriving unit 205 ofthe moving picture decoding device add these merge candidates to themerge candidate list in the same predetermined procedure on the coderand decoder sides. The inter-prediction information deriving unit 104 ofthe moving picture coding device determines the merge index foridentifying the elements of the merge candidate list to perform codingwith the aid of the second bitstream constructing unit 110. Theinter-prediction information deriving unit 205 of the moving picturedecoding device receives the merge index decoded by the second bitstreamdecoder 202, selects the prediction block corresponding to the mergeindex from the merge candidate list, and performs motion-compensatedprediction using the inter-prediction information such as the predictionmode, the reference index, and the motion vector of the selected mergecandidate.

An inter-prediction information deriving method according to a firstpractical example of the embodiment will be described with reference tothe drawings. FIG. 12 is a diagram illustrating a detailed configurationof the inter-prediction information deriving unit 104 of the movingpicture coding device illustrated in FIG. 1 according to the firstpractical example of the embodiment. FIG. 13 is a diagram illustrating adetailed configuration of the inter-prediction information deriving unit205 of the moving picture decoding device illustrated in FIG. 2according to the first practical example of the embodiment.

Portions surrounded by a frame depicted by a solid bold line in FIGS. 12and 13 indicate the inter-prediction information deriving unit 104 andthe inter-prediction information deriving unit 205, respectively.

Further, the portions surrounded by a bold dot line inside the framesindicate a merge candidate list constructing unit 120 of the movingpicture coding device and a merge candidate list constructing unit 220of the moving picture decoding device, which derive merge candidates toconstruct a merge candidate list. The same is provided in a movingpicture decoding device corresponding to the moving picture codingdevice of the embodiment so that the same determination resultconsistent in coding and decoding is obtained.

In an inter-prediction information deriving method according to theembodiment, in a merge candidate deriving process and a merge candidatelist constructing process of the merge candidate list constructing unit120 of the moving picture coding device and the merge candidate listconstructing unit 220 of the moving picture decoding device, mergecandidates of a processing target prediction block are derived and amerge candidate list is constructed without referring to a predictionblock included in the same coding block as a coding block that includesthe processing target prediction block. By doing so, when the partitionmode (PartMode) of a coding block is not 2N×2N partition (PART_2N×2N)(that is, when a plurality of prediction blocks is present in a codingblock), the coder can perform the merge candidate deriving process andthe merge candidate list constructing process in parallel for eachprediction block in a coding block.

The parallel process of deriving the merge candidate list of eachprediction block in a coding block will be described for each partitionmode (PartMode) with reference to FIGS. 14A to 14H. FIGS. 14A to 14H arediagrams for describing a prediction block neighboring to a processingtarget prediction block for each partition mode (PartMode) of aprocessing target coding block. In FIGS. 14A to 14H, A0, B0, C0, D0, andE0 indicate a prediction block A neighboring to the left side, aprediction block B neighboring to the upper side, a prediction block Cneighboring to the top-right corner, a prediction block D neighboring tothe bottom-left corner, and a prediction block E neighboring to thetop-left corner of each processing target prediction block of which thepartition index PartIdx is 0, respectively. Moreover, A1, B1, C1, D1,and E1 indicate a prediction block A neighboring to the left side, aprediction block B neighboring to the upper side, a prediction block Cneighboring to the top-right corner, a prediction block D neighboring tothe bottom-left corner, and a prediction block E neighboring to thetop-left corner of each processing target prediction block of which thepartition index PartIdx is 1, respectively. Moreover, A2, B2, C2, D2,and E2 indicate a prediction block A neighboring to the left side, aprediction block B neighboring to the upper side, a prediction block Cneighboring to the top-right corner, a prediction block D neighboring tothe bottom-left corner, and a prediction block E neighboring to thetop-left corner of each processing target prediction block of which thepartition index PartIdx is 2, respectively. Further, A3, B3, C3, D3, andE3 indicate a prediction block A neighboring to the left side, aprediction block B neighboring to the upper side, a prediction block Cneighboring to the top-right corner, a prediction block D neighboring tothe bottom-left corner, and a prediction block E neighboring to thetop-left corner of each processing target prediction block of which thepartition index PartIdx is 3, respectively.

FIGS. 14B, 14C, and 14D are diagrams illustrating neighboring predictionblocks when the partition mode (PartMode) of partitioning a processingtarget coding block into two prediction blocks arranged in the verticaldirection is 2N×N partition (PART_2N×N), 2N×nU partition (PART_2N×nU),and 2N×nD partition (PART_2N×nD), respectively. A prediction block B1neighboring to a processing target prediction block having the PartIdx 1is a prediction block having the PartIdx 0. Thus, when the mergecandidate deriving process and the merge candidate list constructingprocess are performed for the prediction block having the PartIdx 1 byreferring to the prediction block B1, the processes cannot be performedunless the merge candidate deriving process and the merge candidate listconstructing process for the prediction block having the PartIdx 0belonging to the same coding block which is the prediction block B1 andthe merge candidates to be used are specified. Thus, in theinter-prediction information deriving method according to theembodiment, when the partition mode (PartMode) is 2N×N partition(PART_2N×N), 2N×nU partition (PART_2N×nU), and 2N×nD partition(PART_2N×nD) and PartIdx of the processing target prediction block is 1,by performing the merge candidate deriving process and the mergecandidate list constructing process for the prediction block having thePartIdx 1 without referring to the prediction block B1 which is theprediction block having the PartIdx 0, it is possible to perform themerge candidate deriving process and the merge candidate listconstructing process for two prediction blocks in the coding block inparallel.

FIGS. 14E, 14F, and 14G are diagrams illustrating neighboring predictionblocks when the partition mode (PartMode) of partitioning a processingtarget coding block into two prediction blocks arranged in thehorizontal direction is N×2N partition (PART_N×2N), nL×2N partition(PART_nL×2N), and nR×2N partition (PART_nR×2N), respectively. Aprediction block A1 neighboring to a processing target prediction blockhaving the PartIdx 1 is a prediction block having the PartIdx 0. Thus,when the merge candidate deriving process and the merge candidate listconstructing process are performed for the prediction block having thePartIdx 1 by referring to the prediction block A1, the processes cannotbe performed unless the merge candidate deriving process and the mergecandidate list constructing process for the prediction block having thePartIdx 0 belonging to the same coding block which is the predictionblock A1 and the merge candidates to be used are specified. Thus, in theinter-prediction information deriving method according to theembodiment, when the partition mode (PartMode) is N×2N partition(PART_N×2N), nL×2N partition (PART_nL×2N), and nR×2N partition(PART_nR×2N) and PartIdx of the processing target prediction block is 1,by performing the merge candidate deriving process and the mergecandidate list constructing process for the prediction block having thePartIdx 1 without referring to the prediction block A1 which is theprediction block having the PartIdx 0, it is possible to perform themerge candidate deriving process and the merge candidate listconstructing process for two prediction blocks in the coding block inparallel.

FIG. 14H is a diagram illustrating neighboring prediction blocks whenthe partition mode (PartMode) of partitioning a processing target codingblock into four prediction blocks in both vertical and horizontaldirections is N×N partition (PART_N×N). A prediction block A1neighboring to a processing target prediction block having the PartIdx 1is a prediction block having the PartIdx 0. Thus, when the mergecandidate deriving process and the merge candidate list constructingprocess are performed for the prediction block having the PartIdx 1 byreferring to the prediction block A1, the processes cannot be performedunless the merge candidate deriving process and the merge candidate listconstructing process for the prediction block having the PartIdx 0belonging to the same coding block which is the prediction block A1 arecompleted and the merge candidates to be used are specified. Thus, inthe inter-prediction information deriving method according to theembodiment, when the partition mode (PartMode) is N×N partition(PART_N×N) and PartIdx of the processing target prediction block is 1,by performing the merge candidate deriving process and the mergecandidate list constructing process for the prediction block having thePartIdx 1 without referring to the prediction block A1 which is theprediction block having the PartIdx 0, it is possible to perform themerge candidate deriving process and the merge candidate listconstructing process for respective prediction blocks in the codingblock in parallel. A prediction block B2 neighboring to a processingtarget prediction block having the PartIdx 2 is a prediction blockhaving the PartIdx 0, and a prediction block C2 is a prediction blockhaving the PartIdx 1. Thus, when the merge candidate deriving processand the merge candidate list constructing process are performed for theprediction block having the PartIdx 2 by referring to the predictionblocks B2 and C2, the processes cannot be performed unless the mergecandidate deriving process and the merge candidate list constructingprocess for the prediction blocks having the PartIdx 0 and 1 belongingto the same coding blocks which are the prediction blocks B2 and C2 arecompleted and the merge candidates to be used are specified. Thus, inthe inter-prediction information deriving method according to theembodiment, when the partition mode (PartMode) is N×N partition(PART_N×N) and PartIdx of the processing target prediction block is 2,by performing the merge candidate deriving process and the mergecandidate list constructing process for the prediction block having thePartIdx 2 without referring to the prediction blocks B2 and C2 which arethe prediction blocks having the PartIdx 0 and 1, it is possible toperform the merge candidate deriving process and the merge candidatelist constructing process for respective prediction blocks in the codingblock in parallel. A prediction block E3 neighboring to a processingtarget prediction block having the PartIdx 3 is a prediction blockhaving the PartIdx 0, a prediction block B3 is a prediction block havingPartIdx 1, and a prediction block A3 is a prediction block having thePartIdx 2. Thus, when the merge candidate deriving process and the mergecandidate list constructing process are performed for the predictionblock having the PartIdx 3 by referring to the prediction blocks E3, B3,and A3, the processes cannot be performed unless the merge candidatederiving process and the merge candidate list constructing process forthe prediction blocks having the PartIdx 0, 1, and 2 belonging to thesame coding blocks which are the prediction blocks E3, B3, and A3 arecompleted and the merge candidates to be used are specified. Thus, inthe inter-prediction information deriving method according to theembodiment, when the partition mode (PartMode) is N×N partition(PART_N×N) and PartIdx of the processing target prediction block is 3,by performing the merge candidate deriving process and the mergecandidate list constructing process for the prediction block having thePartIdx 3 without referring to the prediction blocks E3, B3, and A3which are the prediction blocks having the PartIdx 0, 1, and 2, it ispossible to perform the merge candidate deriving process and the mergecandidate list constructing process for respective prediction blocks inthe coding block in parallel.

The inter-prediction information deriving unit 104 of the moving picturecoding device illustrated in FIG. 12 includes a merge candidate listconstructing unit 130, a spatial merge candidate constructing unit 131,a temporal merge candidate reference index deriving unit 132, a temporalmerge candidate deriving unit 133, an additional merge candidatederiving unit 134, a merge candidate limiting unit 136, and aninter-prediction information selecting unit 137.

The inter-prediction information deriving unit 205 of the moving picturedecoding device illustrated in FIG. 13 includes a merge candidate listconstructing unit 230, a spatial merge candidate constructing unit 231,a temporal merge candidate reference index deriving unit 232, a temporalmerge candidate deriving unit 233, an additional merge candidatederiving unit 234, a merge candidate limiting unit 236, and aninter-prediction information selecting unit 237.

FIG. 15 is a flowchart for describing the flow of a merge candidatederiving process and a merge candidate list constructing process whichare the common functions of the merge candidate list constructing unit120 of the inter-prediction information deriving unit 104 of the movingpicture coding device and the merge candidate list constructing unit 220of the inter-prediction information deriving unit 205 of the movingpicture decoding device according to the first practical example of theembodiment of the present invention.

Hereinafter, the respective processes will be described in sequence. Inthe following description, although a case where the slice typeslice_type is B-slice is described unless otherwise set forth, the samecan be applied to P-slice. However, when the slice type slice_type isP-slice, since the inter-prediction mode includes L0 prediction(Pred_L0) only and does not include L1 prediction (Pred_L1) andbi-prediction (Pred_BI), processes associated with L1 can be omitted. Inthe present embodiment, in the moving picture coding device and themoving picture decoding device, when the value of the largest number ofmerge candidates maxNumMergeCand is 0, the merge candidate derivingprocess and the merge candidate list constructing process of FIG. 15 canbe omitted.

First, the merge candidate list constructing unit 130 of theinter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 230 of theinter-prediction information deriving unit 205 of the moving picturedecoding device create a merge candidate list mergeCandList (step S100of FIG. 15). The merge candidate list mergeCandList has a list structureand includes a merge index indicating the locations in the mergecandidate list and a storage area that stores a merge candidatecorresponding to an index as an element. The merge index number startswith 0, and a merge candidate is stored in the storage area of the mergecandidate list mergeCandList. In the following process, a predictionblock serving as a merge candidate corresponding to a merge index iadded to the merge candidate list mergeCandList is expressed asmergeCandList[i] so as to distinguish the arrangement notation frommerge candidate list mergeCandList. In the present embodiment, it isassumed that the merge candidate list mergeCandList can add at leastfive merge candidates (inter-prediction information). Further, 0 is setto a variable numMergeCand indicating the number of merge candidatesadded to the merge candidate list mergeCandList. The created mergecandidate list mergeCandList is supplied to the spatial merge candidateconstructing unit 131 of the inter-prediction information deriving unit104 of the moving picture coding device and the spatial merge candidateconstructing unit 231 of the inter-prediction information deriving unit205 of the moving picture decoding device.

The spatial merge candidate constructing unit 131 of theinter-prediction information deriving unit 104 of the moving picturecoding device and the spatial merge candidate constructing unit 231 ofthe inter-prediction information deriving unit 205 of the moving picturedecoding device derive spatial merge candidates A, B, C, D, and E fromthe respective prediction blocks A, B, C, D, and E neighboring to thecoding/decoding target block from the coding information stored in thecoding information storage memory 115 of the moving picture codingdevice or the coding information storage memory 210 of the movingpicture decoding device and add the derived spatial merge candidates tothe merge candidate list mergeCandList (step S101 of FIG. 15). Here, Nindicating A, B, C, D, E, or anyone of the temporal merge candidates Colis defined. A flag availableFlagN indicating whether inter-predictioninformation of a prediction block N can be used as a spatial mergecandidate N, a L0 reference index refIdxL0N and a L1 reference indexrefIdxL1N of the spatial merge candidate N, a L0 prediction flagpredFlagL0N indicating whether or not to perform L0 prediction, a L1prediction flag predFlagL1N indicating whether or not to perform L1prediction, a L0 motion vector mvL0N, and a L1 motion vector mvL1N arederived. However, in the present embodiment, since merge candidates arederived without referring to a prediction block included in the samecoding block as the coding block that includes a processing targetprediction block, the spatial merge candidates included in the samecoding block as the coding block that includes the processing targetprediction block are not derived. The flow of a detailed process of stepS101 will be described later with reference to the flowchart of FIG. 16.The merge candidate list mergeCandList is supplied to the temporal mergecandidate deriving unit 133 of the inter-prediction information derivingunit 104 of the moving picture coding device and the temporal mergecandidate deriving unit 233 of the inter-prediction information derivingunit 205 of the moving picture decoding device.

Subsequently, the temporal merge candidate reference index deriving unit132 of the inter-prediction information deriving unit 104 of the movingpicture coding device and the temporal merge candidate reference indexderiving unit 232 of the inter-prediction information deriving unit 205of the moving picture decoding device derive the reference indice oftemporal merge candidates from prediction blocks neighboring to thecoding/decoding target block and supply the derived reference indice tothe temporal merge candidate deriving unit 133 of the inter-predictioninformation deriving unit 104 of the moving picture coding device andthe temporal merge candidate deriving unit 233 of the inter-predictioninformation deriving unit 205 of the moving picture decoding device(step S102 of FIG. 15). However, in the present embodiment, thereference indice of temporal merge candidates are derived withoutreferring to a prediction block included in the same coding block as thecoding block that includes the processing target prediction block. Whenthe slice type slice_type is P-slice and the inter-prediction isperformed using the inter-prediction information of the temporal mergecandidates, only the L0 reference indice only are derived since L0prediction (Pred_L0) only is performed. When the slice type slice_typeis B-slice and the inter-prediction is performed using theinter-prediction information of temporal merge candidates, L0 and L1reference indice are derived since bi-prediction (Pred_BI) is performed.The flow of a detailed process of step S102 will be described in detaillater with reference to the flowchart of FIG. 18.

Subsequently, the temporal merge candidate deriving unit 133 of theinter-prediction information deriving unit 104 of the moving picturecoding device and the temporal merge candidate deriving unit 233 of theinter-prediction information deriving unit 205 of the moving picturedecoding device derive temporal merge candidates from pictures ofdifferent time and add the derived temporal merge candidates to themerge candidate list mergeCandList (step S103 of FIG. 15). A flagavailable FlagCol indicating whether temporal merge candidates can beused, a L0 prediction flag predFlagL0Col indicating whether L0prediction is performed, a L1 prediction flag predFlagL1Col indicatingwhether L1 prediction is performed, a L0 motion vector mvL0N, and a L1motion vector mvL1N are derived. The flow of a detailed process of stepS103 will be described in detail later with reference to the flowchartof FIG. 19. The merge candidate list mergeCandList is supplied to theadditional merge candidate deriving unit 134 of the inter-predictioninformation deriving unit 104 of the moving picture coding device andthe additional merge candidate deriving unit 234 of the inter-predictioninformation deriving unit 205 of the moving picture decoding device.

Subsequently, the additional merge candidate deriving unit 134 of theinter-prediction information deriving unit 104 of the moving picturecoding device and the additional merge candidate deriving unit 234 ofthe inter-prediction information deriving unit 205 of the moving picturedecoding device derive additional merge candidates using the largestnumber of merge candidates maxNumMergeCand as an upper limit when thenumber of merge candidates numMergeCand added to the merge candidatelist mergeCandList is smaller than the largest number of mergecandidates maxNumMergeCand and add the derived additional mergecandidates to the merge candidate list mergeCandList (step S104 of FIG.15). Using the largest number of merge candidates maxNumMergeCand as anupper limit, for the P-slices, merge candidates which have differentreference indice and of which the motion vector has the value (0, 0) andthe prediction mode is L0 prediction (Pred_L0) are added. For theB-slices, merge candidates which have different reference indice and ofwhich the motion vector has the value (0, 0) and the prediction mode isbi-prediction (Pred_BI) are added. The flow of a detailed process ofstep S104 will be described in detail later with reference to theflowchart of FIG. 26. For the B-slices, merge candidates which have beenadded and of which the combinations of L0 prediction and L1 predictionare changed and the prediction mode is bi-prediction (Pred_BI) may bederived and added. The merge candidate list mergeCandList is supplied tothe merge candidate limiting unit 136 of the inter-predictioninformation deriving unit 104 of the moving picture coding device andthe merge candidate limiting unit 236 of the inter-predictioninformation deriving unit 205 of the moving picture decoding device.

Subsequently, the merge candidate limiting unit 136 of theinter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate limiting unit 236 of theinter-prediction information deriving unit 205 of the moving picturedecoding device limit the value of the number of merge candidatesnumMergeCand added to the merge candidate list mergeCandList to thelargest number of merge candidates maxNumMergeCand when the value of thenumber of merge candidates numMergeCand added to the merge candidatelist mergeCandList is larger than the largest number of merge candidatesmaxNumMergeCand (step S106 of FIG. 15). The merge candidate listmergeCandList is supplied to the inter-prediction information selectingunit 137 of the inter-prediction information deriving unit 104 of themoving picture coding device and the inter-prediction informationselecting unit 237 of the inter-prediction information deriving unit 205of the moving picture decoding device. The flow of a detailed process ofstep S106 will be described with reference to the flowchart of FIG. 27.

When the value of the number of merge candidates numMergeCand added tothe merge candidate list mergeCandList is larger than the largest numberof merge candidates maxNumMergeCand (step S7101 of FIG. 27: YES), thevalue of the number of merge candidates numMergeCand is updated to thelargest number of merge candidates maxNumMergeCand (step S7102 of FIG.27). The process of step S7102 means inhibiting accesses to all mergecandidates of which the merge index in the merge candidate listmergeCandList is larger than (maxNumMergeCand−1) and limiting the numberof merge candidates added to the merge candidate list mergeCandList tothe largest number of merge candidates maxNumMergeCand.

In the present embodiment, the number of merge candidates added to themerge candidate list mergeCandList is set to a fixed number inrespective slices. The reason why the number of merge candidates addedto the merge candidate list mergeCandList is fixed is as follows. If thenumber of merge candidates added to the merge candidate listmergeCandList changes depending on the state of the constructed mergecandidate list, entropy decoding depends on the constructed mergecandidate list. Thus, the decoder cannot decode merge indice by entropydecoding unless a merge candidate list is constructed for respectiveprediction blocks and the number of merge candidates added to the mergecandidate list mergeCandList is derived. As a result, decoding of mergeindice is delayed and entropy decoding becomes complex. Further, ifentropy decoding depends on the state of a constructed merge candidatelist that includes merge candidates Col derived from prediction blocksof pictures of different time, when an error occurs during decoding of abitstream of a different picture, a bitstream of the current picture isalso influenced by the error. Thus, it is not possible to derive thenumber of merge candidates added to a normal merge candidate listmergeCandList and to continue entropy decoding properly. As in thepresent embodiment, when the number of merge candidates added to themerge candidate list mergeCandList is set to a fixed value forrespective slices, it is not necessary to derive the number of mergecandidates added to the merge candidate list mergeCandList in respectiveprediction blocks and it is possible to decode merge indice by entropydecoding independently from construction of the merge candidate list.Moreover, even if an error occurs during decoding of a bitstream ofanother picture, it is possible to continue entropy decoding of abitstream of the current picture without being influenced by the error.In the present embodiment, a syntax element indicating the number ofmerge candidates added to the merge candidate list mergeCandList iscoded for respective slices, and the number of merge candidates added tothe mergeCandList is defined as the largest number of merge candidatesmaxNumMergeCand.

Subsequently, a method of deriving merge candidates N from predictionblocks N neighboring to a coding/decoding target block, which is theprocess of step S101 of FIG. 15 will be described in detail. FIG. 16 isa flowchart for describing the flow of a spatial merge candidatederiving process of step S101 of FIG. 15. N is a variable A (left), B(upper), C (top-right), D (bottom-left), or E (top-left) indicating theregion of a neighboring prediction block. In the present embodiment,four spatial merge candidates at most are derived from five neighboringprediction blocks.

In FIG. 16, the coding information of a prediction block A neighboringto the left side of a coding/decoding target prediction block using thevariable N set to A is investigated to derive a merge candidate A, thecoding information of a prediction block B neighboring to the left sideof a coding/decoding target prediction block using the variable N set toB is investigated to derive a merge candidate B, the coding informationof a prediction block C neighboring to the left side of acoding/decoding target prediction block using the variable N set to C isinvestigated to derive a merge candidate C, the coding information of aprediction block D neighboring to the left side of a coding/decodingtarget prediction block using the variable N set to D is investigated toderive a merge candidate D, and the coding information of a predictionblock E neighboring to the left side of a coding/decoding targetprediction block using the variable N set to E is investigated to derivea merge candidate E. The derived merge candidates are added to the mergecandidate list (steps S1101 to S1118 of FIG. 16).

First, when the variable N is E and the sum of the values of flagsavailableFlagA, availableFlagB, availableFlagC, and availableFlagD is 4(step S1102 of FIG. 16: YES) (that is, four spatial merge candidates arederived), the flag availableFlagE of the merge candidate E is set to 0(step S1107 of FIG. 16), both values of the motion vectors mvL0E andmvL1E of the merge candidate E are set to (0, 0) (step S1108 of FIG.16), both values of the flags predFlagL0E and predFlagL1E of the mergecandidate E are set to 0 (step S1109 of FIG. 16). After that, the flowproceeds to step S1118 and the spatial merge candidate deriving processends.

In the present embodiment, since four merge candidates at most arederived from the neighboring prediction blocks, when four spatial mergecandidates have already been derived, it is not necessary to perform thespatial merge candidate deriving process further.

On the other hand, when the variable N is not E or the sum of the valuesof the flags availableFlagA, availableFlagB, availableFlagC, andavailableFlagD is not 4 (step S1102 of FIG. 16: NO) (that is, fourspatial merge candidates are not derived), the flow proceeds to stepS1103. When the neighboring prediction block N is included in the samecoding block as the coding block that includes the deriving targetprediction block (step S1103 of FIG. 16; YES), the value of the flagavailableFlagN of the merge candidate N is set to 0 (step S1107 of FIG.16), both values of the motion vectors mvL0N and mvL1N of the mergecandidate N are set to (0, 0) (step S1108 of FIG. 16), both values ofthe flags predFlagL0N and predFlagL1N of the merge candidate N are setto 0 (step S1109 of FIG. 16), and then, the flow proceeds to step S1118.When the neighboring prediction block N is included in the same codingblock as the coding block that includes the deriving target predictionblock (step S1103 of FIG. 16: YES), the neighboring prediction block Nis not referred to so that the prediction block merge candidate derivingprocess and the merge candidate list constructing process can beperformed in parallel.

Specifically, the neighboring prediction block B of which the partitionmode (PartMode) is 2N×N partition (PART_2N×N), 2N×nU partition(PART_2N×nU), or 2N×nD partition (PART_2N×nD) and the PartIdx of theprocessing target prediction block is 1 is the case that the neighboringprediction block N is included in the same coding block as the codingblock that includes the deriving target prediction block. In this case,since the neighboring prediction block B is a prediction block havingthe PartIdx 0, the neighboring prediction block B is not referred to sothat the prediction block merge candidate deriving process and the mergecandidate list constructing process can be performed in parallel.

Further, the neighboring prediction block A of which the partition mode(PartMode) is N×2N partition ((PART_N×2N), nL×2N partition (PART_nL×2N),or nR×2N partition (PART_nR×2N) and the PartIdx of the processing targetprediction block is 1 is the case that the neighboring prediction blockN is included in the same coding block as the coding block that includesthe deriving target prediction block. In this case, since theneighboring prediction block A is the prediction block having thePartIdx 0, the neighboring prediction block A is not referred to so thatthe prediction block merge candidate deriving process and the mergecandidate list constructing process can be performed in parallel.

Further, when the partition mode (PartMode) is N×N partition (PART_N×N)and the PartIdx of the processing target prediction block is 1, 2, or 3,the neighboring prediction block N may be included in the same codingblock as the coding block that includes the deriving target predictionblock.

On the other hand, when the neighboring prediction block N is notincluded the same coding block that includes the processing targetprediction block (step S1103 of FIG. 16: NO), the prediction blocks Nneighboring to the coding/decoding target prediction block arespecified, and when the respective prediction blocks N can be used, thecoding information of the prediction blocks N is acquired from thecoding information storage memory 115 or 210 (step S1104 of FIG. 16).

When the neighboring prediction block N cannot be used (step S1105 ofFIG. 16: NO) or the prediction mode PredMode of the prediction block Nis intra-prediction (MODE_INTRA) (step S1106 of FIG. 16: NO), the valueof the flag availableFlagN of the merge candidate N is set to 0 (stepS1107 of FIG. 16), both values of the motion vectors mvL0N and mvL1N ofthe merge candidate N are set to (0, 0) (step S1108 of FIG. 16), andboth values of the flags predFlagL0N and predFlagL1N of the mergecandidate N are set to 0 (step S1109). Then, the flow proceeds to stepS1118. Here, specific examples of the case where the neighboringprediction block N cannot be used include a case where the neighboringprediction block N is positioned outside a coding/decoding target sliceand a case where a coding/decoding process is not completed because theneighboring prediction block N is later in the order of thecoding/decoding process.

On the other hand, when the neighboring prediction block N is outsidethe same coding block as the coding block of the deriving targetprediction block (step S1104 of FIG. 16: YES), the neighboringprediction block N can be used (step S1105 of FIG. 16: YES), and theprediction mode PredMode of the prediction block N is not theintra-prediction (MODE_INTRA) (step S1106 of FIG. 16: YES), theinter-prediction information of the prediction block N is used as theinter-prediction information of the merge candidate N. The value of theflag availableFlagN of the merge candidate N (step S1110 of FIG. 16) isset to 1, the motion vectors mvL0N and mvL1N of the merge candidate Nare set to the same values of the motion vectors mvL0N [xN][yN] andmvL1N [xN][yN] of the motion vectors of the prediction block N (stepS1111 of FIG. 16), the reference indice refIdxL0N and refIdxL1N of themerge candidate N are set to the same values as the reference indicerefIdxL0[xN][yN] and refIdxL1[xN][yN] of the prediction block N (stepS1112 of FIG. 16), and the flags predFlagL0N and predFlagL1N of themerge candidate N are set to the flags predFlagL0[xN][yN] andpredFlagL1[xN][yN] of the prediction block N (step S1113 of FIG. 16).Here, xN and yN are indice indicating the position of a pixel at thetop-left corner of the prediction block N in the picture.

Subsequently, the flags predFlagL0N and predFlagL1N of the mergecandidate N, the reference indice refIdxL0N and refIdxL1N of the mergecandidate N, and the motion vectors mvL0N and mvL1N of the mergecandidate N are compared with those of the merge candidates which havebeen derived (step S1114: FIG. 16). When the same merge candidate is notpresent (step S1115 of FIG. 16: YES), the merge candidate N is added tothe position at which the merge index of the merge candidate listmergeCandList has the same value as numMergeCand (step S1116 of FIG. 16)and the number of merge candidates numMergeCand is incremented by 1(step S1117 of FIG. 16). On the other hand, when the same mergecandidate is present (step S1115 of FIG. 16: NO), steps S1116 and S1117are skipped and the flow proceeds to step S1118.

The processes of steps S1102 to S1117 are repeatedly performed for N=A,B, C, D, and E (steps S1101 to S1118 of FIG. 16).

Next, a method of deriving the reference indice of temporal mergecandidates of step S102 of FIG. 15 will be described in detail. The L0and L1 reference indice of the temporal merge candidates are derived.

In the present embodiment, the reference indice of the temporal mergecandidates are derived using the reference indice of spatial mergecandidates (that is, the reference indice used in the prediction blocksneighboring to the coding/decoding target block). This is because when atemporal merge candidate is selected, the reference index of thecoding/decoding target prediction block has high correlation with thereference index of the prediction blocks neighboring to thecoding/decoding target block which becomes the spatial merge candidate.In particular, in the present embodiment, the reference indice only ofthe prediction block A neighboring to the left side of thecoding/decoding target prediction block are used. This is because theprediction blocks A and B neighboring to the side of the coding/decodingtarget prediction block among the neighboring prediction blocks A, B, C,D, and E which are also spatial merge candidates have higher correlationthan the prediction blocks C, D, and E neighboring to the corner of thecoding/decoding target prediction block. Since the prediction blocks C,D, and E having relatively low correlation are not used and theprediction blocks to be used are limited to the prediction block A, itis possible to improve the coding efficiency resulting from deriving ofthe reference indice of temporal merge candidates and to reduce theprocessing amount and the memory access amount associated with theprocess of deriving the reference indice of temporal merge candidates.

FIGS. 17A to 17H are diagrams illustrating neighboring blocks referredto in the temporal merge candidate reference index deriving process ofthe present embodiment. In the present embodiment, whether or not torefer to the prediction block neighboring to the left side of thederiving target prediction block is changed according to the partitionindex PartIdx of the prediction block regardless of the partition mode(PartMode) of a coding block. When the partition index PartIdx of theprediction block is 0, the prediction block neighboring to the left sideis referred to. When the partition index PartIdx is not 0, theneighboring prediction block is not referred to but a default value isused. When the partition index PartIdx of the prediction block is 0, inany partition mode (PartMode), the prediction block neighboring to theleft side does always not belong to the coding block. When the partitionindex PartIdx of the prediction block is not 0, the prediction blockneighboring to the left side belongs to the coding block depending onthe partition mode (PartMode). When the partition mode (PartMode) is2N×2N partition (PART_2N×2N), as illustrated in FIG. 17A, a predictionblock A0 neighboring to the left side of the deriving target predictionblock is referred to, and the LX reference index of the temporal mergecandidate is set to the value of the LX reference index of theprediction block A0.

When the partition mode (PartMode) of partitioning a processing targetcoding block into two prediction blocks arranged in the verticaldirection is 2N×N partition (PART_2N×N), 2N×nU partition (PART_2N×nU),and 2N×nD partition (PART_2N×nD) and the partition mode (PartMode) ofpartitioning a processing target coding block into two prediction blockarranged in the horizontal direction is N×2N partition ((PART_N×2N),nL×2N partition (PART_nL×2N), and nR×2N partition (PART_nR×2N), asillustrated in FIGS. 17B, 17C, 17D, 17E, 17F, and 17G, the predictionblock A0 neighboring to the left side is referred to in the predictionblock of which the partition index PartIdx is 0, and the LX referenceindex of the temporal merge candidate is set to the value of the LXreference index of the prediction block A0. The neighboring predictionblock is not referred to in the prediction block of which the partitionindex PartIdx of the deriving target is 1, and the LX reference index ofthe temporal merge candidate is set to the default value 0. Since theprediction block A0 to be referred to does not belong to the codingblock, the reference indice of the temporal merge candidates of twoprediction blocks of which the partition indice PartIdx are 0 and 1 canbe derived in parallel.

When the partition mode (PartMode) of partitioning a processing targetcoding block into four prediction blocks in vertical and horizontaldirections is N×N partition (PART_N×N), as illustrated in FIG. 17H, theprediction block A0 neighboring to the left side is referred to in theprediction block of which the deriving target partition index PartIdx is0, the LX reference index of the temporal merge candidate is set to thevalue of the LX reference index of the prediction block A0. In theprediction blocks of which the deriving target partition indice PartIdxare 1, 2, and 3, the neighboring prediction block is not referred to,and the LX reference index of the temporal merge candidate is set to thedefault value 0. Since the prediction block A0 to be referred to doesnot belong to the coding block, the reference indice of the temporalmerge candidates of four prediction blocks of which the partition indicePartIdx are 0, 1, 2, and 3 are derived in parallel.

However, when the neighboring prediction block A does not perform LXprediction, the value of the LX refractive index of the temporal mergecandidate is set to the default value 0. The reason why the defaultvalue of the LX reference index of the temporal merge candidate is setto 0 when the neighboring prediction block A does not perform LXprediction and the partition index PartIdx of the deriving targetprediction block is 1 is because the reference picture of which thevalue of the reference index in inter-prediction is 0 is most probableto be selected. However, the present invention is not limited to this,the default value of the reference index may be a value (1, 2, or thelike) other than 0, and a syntax element indicating the default value ofthe reference index may be provided in a bitstream in sequence, picture,or slice levels and be transmitted so that the default value can beselected on the coder side.

FIG. 18 is a flowchart for describing the flow of a temporal mergecandidate reference index deriving process of step S102 of FIG. 15according to the present embodiment. First, when the partition indexPartIdx is 0 (step S2104: YES), the coding information of the predictionblock A neighboring to the left side of the deriving target predictionblock is acquired from the coding information storage memory 115 or 210(step S2111).

The subsequent processes of steps S2113 to S2115 are performed in therespective lists L0 and L1 (steps S2112 to S2116). LX is set to L0 whenthe L0 reference index of the temporal merge candidate is derived and LXis set to L1 when the L1 reference index of the temporal merge candidateis derived. However, when the slice_type slice_type is P-slice, sincethe inter-prediction mode includes L0 prediction (Pred_L0) only and doesnot include L1 prediction (Pred_L1) and bi-prediction (Pred_BI),processes associated with L1 can be omitted.

When the flag predFlagLX[xA][yA] indicating whether or not to perform LXprediction of the prediction block A is not 0 (step S2113: YES), the LXreference index refIdxLXCol of the temporal merge candidate is set tothe same value as the value of the LX reference index refIdxLX[xA][yA]of the prediction block A (step S2114). Here, xA and yA are indiceindicating the position of a pixel at the top-left corner of theprediction block A in the picture.

In the present embodiment, in the prediction block N (N=A, B), when theprediction block N is outside the coding/decoding target slice andcannot be used, when the prediction block N is later than thecoding/decoding target prediction block in the coding/decoding order andcannot be used if it is coded/decoded, or when the prediction modePredMode of the prediction block N is intra-prediction (MODE_INTRA),both the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction and the flag predFlagL1[xN][yN] indicating whether or not touse L1 prediction of the prediction block N are 0. Here, xN and yN areindice indicating the position of a pixel at the top-right corner of theprediction block N in the picture. When the prediction mode PredMode ofthe prediction block N is inter-prediction (MODE_INTER) and theinter-prediction mode is L0 prediction (Pred_L0), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 1 and the flag predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction is 0. When the inter-prediction modeof the prediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0 and the flag predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction is 1. When the inter-prediction modeof the prediction block N is bi-prediction (Pred_BI), both the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N and the flag predFlagL1[xN][yN] indicating whether ornot to use L1 prediction are 1.

When the flag predFlagLX[xA][yA] indicating whether or not to perform LXprediction of the prediction block A is 0 (step S2113: NO), the LXreference index refIdxLXCol of the temporal merge candidate is set tothe default value 0 (step S2115).

The processes of steps S2113 to S2115 are performed for each of L0 andL1 (steps S2112 to S2116), and the reference index deriving processends.

On the other hand, when the partition index PartIdx is not 0 (stepS2104: NO), the subsequent process of step S2121 is performed for eachof L0 and L1 (steps S2118 to S2122). LX is set to L0 when the L0reference index of the temporal merge candidate is to be derived, and LXis set to L1 when the L1 reference index is to be derived. However, whenthe slice_type slice_type is P-slice, since the inter-prediction modeincludes L0 prediction (Pred_L0) only and does not include L1 prediction(Pred_L1) and bi-prediction (Pred_BI), the processes associated with L1can be omitted.

The LX reference index refIdxLXCol of the temporal merge candidate isset to the default value 0 (step S2121).

The processes up to step S2121 are performed for each of L0 and L1(steps S2118 to S2122), and the reference index deriving process ends.

In the present embodiment, although whether or not to refer to theprediction block neighboring to the left side of the deriving targetprediction block is switched, whether or not to refer to the predictionblock neighboring to the upper side may be switched instead of theprediction block neighboring to the left side.

Next, a method of deriving merge candidates of different time in stepS103 of FIG. 15 will be described in detail. FIG. 19 is a flowchart fordescribing the flow of a temporal merge candidate deriving process ofstep S103 of FIG. 15.

First, a picture colPic of different time is derived using a flagcollocated_from_l0_flag indicating whether the picture colPic ofdifferent time used when deriving the slice_type slice_type described inthe slice header in respective slices and a motion vector predictorcandidate in a temporal direction, or a merge candidate uses a referencepicture added to any one of the L0 reference list or L1 reference listof a picture in which the processing target prediction block is included(step S3101).

FIG. 20 is a flowchart for describing the flow of a process of derivingthe picture colPic of different time in step S3101 of FIG. 19. When theslice_type slice_type is B-slice and the flag collocated_from_l0_flag is0 (step S3201: YES, step S3202: YES), a picture of which theRefPicList1[0] (that is, the reference index of a reference list L1) is0 becomes the picture colPic of different time (step S3203). In othercases, that is, when the slice_type slice_type is B-slice and the flagcollocated_from_l0_flag is 1 (step S3201: YES, step S3202: NO), or whenthe slice_type slice_type is P-slice (step S3201: NO, step S3204: YES),a picture of which the RefPicList0[0] (that is, the reference index ofthe reference list L0) is 0 becomes the picture colPic of different time(step S3205).

Subsequently, the flow returns to the flowchart of FIG. 19, a predictionblock colPU of different time is derived, and coding information isacquired (step S3102).

FIG. 21 is a flowchart for describing the flow of a process of derivinga prediction block colPU of the picture colPic of different time in stepS3102 of FIG. 19.

First, a prediction block positioned on the bottom-right corner(outside) of the same position as the processing target prediction blockin the picture colPic of different time is set as the prediction blockcolPU of different time (step S3301). This prediction block correspondsto the prediction block T0 illustrated in FIG. 9.

Subsequently, the coding information of the prediction block colPU ofdifferent time is acquired (step S3302). When PredMode of the predictionblock colPU of different time cannot be used or the prediction modePredMode of the prediction block colPU of different time isintra-prediction (MODE_INTRA) (step S3303: YES, step S3304: YES), aprediction block positioned at the top-left corner of the center of thesame position as the processing target prediction block in the picturecolPic of different time is set as the prediction block colPU ofdifferent time (step S3305). This prediction block corresponds to theprediction block T1 illustrated in FIG. 9.

Next, the flow returns to the flowchart of FIG. 19, a flagavailableFlagL0Col indicating whether the L0 motion vector predictormvL0Col and the temporal merge candidate Col derived from the predictionblock of a different picture at the same position as the coding/decodingtarget prediction block are valid is derived (step S3103), and a flagavailableFlagL1Col indicating whether the L1 motion vector predictormvL0Col and the temporal merge candidate Col are valid is derived (stepS3104). Further, when the flag availableFlagL0Col or the flagavailableFlagL1Col is 1, the flag availableFlagCol indicating whetherthe temporal merge candidate Col is valid is set to 1.

FIG. 22 is a flowchart for describing the flow of the process ofderiving inter-prediction information of temporal merge candidates insteps S3103 and S3104 of FIG. 19. The temporal merge candidate derivingtarget list L0 or L1 is referred to as LX and prediction using LX isreferred to as LX prediction. The same is true for the followingdescription unless otherwise set forth below. LX is L0 when step S3103which is the deriving process of the list L0 of the temporal mergecandidate is invoked, and LX is L1 when step S3104 which is the derivingprocess of the list L1 of the temporal merge candidate is invoked.

When the prediction mode PredMode of the prediction block colPU ofdifferent time is intra-prediction (MODE_INTRA) or cannot be used (stepS3401: NO, step S3402: NO), it is assumed that temporal merge candidatesare not present. Both the flag availableFlagLXCol and the flagpredFlagLXCol are set to 0 (step S3403), the motion vector mvLXCol isset to (0, 0) (step S3404), and the process of deriving inter-predictioninformation of temporal merge candidates ends.

When the prediction block colPU can be used and the prediction modePredMode is not intra-prediction (MODE_INTRA) (step S3401: YES, stepS3402: YES), mvCol, refIdxCol, and availableFlagCol are derived in thefollowing flow.

When the flag PredFlagL0[xPCol][yPCol] indicating whether L0 predictionof the colPU is used is 0 (step S3405: YES), since the prediction modeof the prediction block colPU is Pred_L1, the motion vector mvCol is setto the same value as MvL1[xPCol][yPCol] which is the L1 motion vector ofthe prediction block colPU (step S3406), the reference index refIdxColis set to the same value as the L1 reference indexRefIdxL1[xPCol][yPCol] (step S3407), and the list ListCol is set to L1(step S3408). Here, xPCol and yPCol are indice indicating the positionof a pixel at the top-left corner of the prediction block colPU in thepicture colPic of different time.

On the other hand, when the L0 prediction flag PredFlagL0[xPCol][yPCol]of the prediction block colPU is not 0 (step S3405 of FIG. 22: NO), itis determined whether the L1 prediction flag PredFlagL1[xPCol][yPCol] ofthe prediction block colPU is 0. When the L1 prediction flagPredFlagL1[xPCol][yPCol] of the prediction block colPU is 0 (step S3409:YES), the motion vector mvCol is set to the same value asMvL0[xPCol][yPCol] which is the L0 motion vector of the prediction blockcolPU (step S3410), the reference index refIdxCol is set to the samevalue as the L0 reference index RefIdxL0[xPCol][yPCol] (step S3411), andthe list ListCol is set to L0 (step S3412).

When both the L0 prediction flag PredFlagL0[xPCol][yPCol] of theprediction block colPU and the L1 prediction flagPredFlagL1[xPCol][yPCol] of the prediction block colPU are not 0 (stepS3405: NO, step S3409: NO), since the inter-prediction mode of theprediction block colPU is bi-prediction (Pred_BI), one of the two L0 andL1 motion vectors is selected (step S3413).

FIG. 23 is a flowchart illustrating the flow of the process of derivinginter-prediction information of temporal merge candidates when theinter-prediction mode of the prediction block colPU is bi-prediction(Pred_BI).

First, it is determined whether the POCs of all pictures added to allreference lists are smaller than the POC of the current coding/decodingtarget picture (step S3501). When the POCs of all pictures added to allreference lists L0 and L1 of the prediction block colPU are smaller thanthe POC of the current coding/decoding target picture (step S3501: YES)and when LX is L0 (that is, the vector predictor candidates of the L0motion vector of the coding/decoding target picture have been derived)(step S3502: YES), the inter-prediction information of the list L0 ofthe prediction block colPU is selected. In this case, when LX is L1(that is, the vector predictor candidates of the L1 motion vector of thecoding/decoding target picture have been derived) (step S3502: NO), theinter-prediction information of the list L1 of the prediction blockcolPU is selected. On the other hand, when at least one of the POCs ofthe pictures added to all reference lists L0 and L1 of the predictionblock colPU is larger than the POC of the current coding/decoding targetpicture (step S3501: NO) and when the flag collocated_from_l0_flag is 0(step S3503: YES), the inter-prediction information of the list L0 ofthe prediction block colPU is selected. In this case, when the flagcollocated_from_l0_flag is 1 (step S3503: NO), the inter-predictioninformation of the list L1 of the prediction block colPU is selected.

When the inter-prediction information of the list L0 of the predictionblock colPU is selected (step 3502: YES, step S3503: YES), the motionvector mvCol is set to the same value as MvL0[xPCol][yPCol] (stepS3504), the reference index refIdxCol is set to the same value asRefIdxL0[xPCol][yPCol] (step S3505), and the list ListCol is set to L0(step S3506).

When the inter-prediction information of the list L1 of the predictionblock colPU is selected (step S3502: NO, step S3503: NO), the motionvector mvCol is set to the same value as MvL1[xPCol][yPCol] (stepS3507), the reference index refIdxCol is set to the same value asRefIdxL1[xPCol][yPCol] (step S3508), and the list ListCol is set to L1(step S3509).

Returning to FIG. 22, if inter-prediction information can be acquiredfrom the prediction block colPU, both the flag availableFlagLXCol andthe flag predFlagLXCol are set to 1 (step S3414).

Subsequently, the motion vector mvCol is scaled to obtain the LX motionvector mvLXCol of the temporal merge candidate (step S3415). The flow ofthis motion vector scaling process will be described with reference toFIGS. 24 and 25.

FIG. 24 is a flowchart illustrating the flow of the motion vectorscaling process of step S3415 of FIG. 22.

The POC of the reference picture corresponding to the reference indexrefIdxCol referred to by the list ListCol of the prediction block colPUis subtracted from the POC of the picture colPic of different time toderive the picture-to-picture distance td (step S3601). When the POC ofthe reference picture referred to by the list ListCol of the predictionblock colPU is earlier in the display order than the picture colPic ofdifferent time, the picture-to-picture distance td has a positive value.When the POC of the reference picture referred to by the list ListCol ofthe prediction block colPU is later in the display order than thepicture colPic of different time, the picture-to-picture distance td hasa negative value.

td=(POC of Picture colPic of different time)−(POC of Reference picturereferred to by List ListCol of Prediction block colPU)

The POC of the reference picture corresponding to the LX reference indexof the temporal merge candidate derived in step S102 of FIG. 15 issubtracted from the POC of the current coding/decoding target picture toderive the picture-to-picture distance tb (step S3602). When thereference picture referred to by the list LX of the currentcoding/decoding target picture is earlier in the display order than thecurrent coding/decoding target picture, the picture-to-picture distancetb has a positive value. When the reference picture referred to by thelist LX of the current coding/decoding target picture is later in thedisplay order than the current coding/decoding target picture, thepicture-to-picture distance tb has a negative value.

tb=(POC of Current coding/decoding target picture)−(POC of Referencepicture corresponding to LX reference index of Temporal merge candidate)

Subsequently, the picture-to-picture distances td and tb are compared(step S3603). When the picture-to-picture distances td and tb are thesame (step S3603: YES), the LX motion vector mvLXCol of the temporalmerge candidate is set to the same value as the motion vector mvCol(step S3604), and the scaling process ends.

mvLXCol=mvCol

On the other hand, when the picture-to-picture distances td and tb arenot the same (step S3603: NO), mvCol is multiplied by a scaling factortb/td according to the following expression to perform the scalingprocess (step S3605) to obtain the scaled LX motion vector mvLXCol ofthe temporal merge candidate.

mvLXCol=tb/td*mvCol

FIG. 25 illustrates an example in which the scaling process of stepS3605 is performed with integer-level accuracy. The processes of stepsS3606 to S3608 of FIG. 25 correspond to the process of step S3605 ofFIG. 24.

First, similarly to the flowchart of FIG. 24, the picture-to-picturedistance td and the picture-to-picture distance tb are derived (stepsS3601 and S3602).

Subsequently, the picture-to-picture distances td and tb are compared(step S3603). When the picture-to-picture distances td and tb are thesame (step S3603: YES), similarly to the flowchart of FIG. 24, the LXmotion vector mvLXCol of the temporal merge candidate is set to the samevalue as the motion vector mvCol (step S3604), and the scaling processends.

mvLXCol=mvCol

On the other hand, when the picture-to-picture distances td and tb arenot the same (step S3603: NO), a variable tx is derived according to thefollowing expression (step S3606).

tx=(16384+Abs(td/2))/td

Subsequently, a scaling factor DistScaleFactor is derived according tothe following expression (step S3607).

DistScaleFactor=(tb*tx+32)>>6

Subsequently, a scaled LX motion vector mvLXCol of the temporal mergecandidate is obtained according to the following expression (stepS3608).

mvLXCol=ClipMv(Sign(DistScaleFactor*mvCol)*((Abs(DistScaleFactor*mvCol)+127)>>8))

Subsequently, returning to the flowchart of FIG. 19, when a temporalmerge candidate is present (step S3105: YES), the temporal mergecandidate is added to the position at which the merge index of the mergecandidate list mergeCandList has the same value as numMergeCand (stepS3106), the number of merge candidates numMergeCand is incremented by 1(step S3107), and the temporal merge candidate deriving process ends. Onthe other hand, when the temporal merge candidate is not present (stepS3105: NO), steps S3106 and S3107 are skipped and the temporal mergecandidate deriving process ends.

Next, a method of deriving additional merge candidates which is theprocess of step S104 of FIG. 15, performed by the additional mergecandidate deriving unit 134 of FIG. 12 and the additional mergecandidate deriving unit 234 of FIG. 13 will be described in detail. FIG.26 is a flowchart for describing the flow of the additional mergecandidate deriving process of step S104 of FIG. 15.

In the additional merge candidate deriving process performed by theadditional merge candidate deriving unit 134 of FIG. 12 and theadditional merge candidate deriving unit 234 of FIG. 13, a plurality ofmerge candidates having different values of inter-prediction informationis derived and added to the merge candidate list in order to broaden thechoices for merge candidates to improve the coding efficiency. Inparticular, in the additional merge candidate deriving process of FIG.26, the values of the prediction mode and the motion vector are fixed,and a plurality of merge candidates having different values of referenceindice is derived and added to the merge candidate list (steps S5101 toS5119 of FIG. 26).

First, when the slice type is P-slice (step S5101 of FIG. 26: YES), thevalue of the number of L0 reference indice is set to a variablenumRefIdx indicating the number of reference indice (step S5102 of FIG.26). On the other hand, when the slice type is no P-slice (step S5101 ofFIG. 26: NO) (that is, when the slice type is B-slice), the smallervalue among the number of L0 reference indice and the number of L1reference indice is set to the variable numRefIdx indicating the numberof reference indice (step S5103 of FIG. 26). Subsequently, 0 is set tothe reference index i (step S5104 of FIG. 26).

Subsequently, an additional merge candidate of which the value of themotion vector of the prediction mode corresponding to the slice type is(0, 0) is derived while changing the reference index i and added to themerge candidate list (steps S5105 to S5119 of FIG. 26).

First, when the number of merge candidates numMergeCand is smaller thanthe largest number of merge candidates maxNumMergeCand (step S5106 ofFIG. 26: YES), the flow proceeds to step S5107. When the number of mergecandidates numMergeCand is not smaller than the largest number of mergecandidates maxNumMergeCand (step S5106 of FIG. 26: NO), the additionalmerge candidate deriving process ends. Subsequently, when the referenceindex i is smaller than the variable numRefIdx (step S5107 of FIG. 26:YES), the flow proceeds to step S5109. When the reference index i is notsmaller than the variable numRefIdx (step S5107 of FIG. 26: NO), theadditional merge candidate deriving process ends.

Subsequently, when the slice type is P-slice (step S5109 of FIG. 26:YES), (0, 0) is set to the motion vectors mvL0Zero and mvL1Zero of theadditional merge candidates (step S5110 of FIG. 26), the value of thereference index i and −1 are set to the reference indice refIdxL0Zeroand refIdxL1Zero of the additional merge candidates, respectively (stepS5111 of FIG. 26), and 1 and 0 are set to the flags predFlagL0Zero andpredFlagL1Zero of the additional merge candidates, respectively (stepS5112 of FIG. 26). Then, the flow proceeds to step S5116.

On the other hand, when the slice type is not P-slice (step S5109 ofFIG. 26: NO) (that is, when the slice type is B-slice), (0, 0) is set tothe motion vectors mvL0Zero and mvL1Zero (step S5113 of FIG. 26), thevalue of the reference index i is set to the reference indicerefIdxL0Zero and refIdxL1Zero of the additional merge candidates (stepS5114 of FIG. 26), and 1 is set to the flags predFlagL0Zero andpredFlagL1Zero of the additional merge candidates (step S5115 of FIG.26). Then, the flow proceeds to step S5116.

Subsequently, the additional merge candidate is added to the position atwhich the merge index of the merge candidate list mergeCandList isindicated by the same value as numMergeCand (step S5116 of FIG. 26), andthe number of merge candidates numMergeCand is incremented by 1 (stepS5117 of FIG. 26). Subsequently, the index i is incremented by 1 (stepS5118 of FIG. 26), and the flow proceeds to step S5119.

The processes of steps S5106 to S5118 are repeatedly performed forrespective reference indice i (steps S5105 to S5119 of FIG. 26).

In FIG. 26, although the values of the prediction mode and the motionvector are fixed and a plurality of merge candidates having differentvalues of reference indice is derived and added to the merge candidatelist, a plurality of merge candidates of different prediction modes maybe derived and added to the merge candidate list, and merge candidateshaving different values of motion vectors may be derived and added tothe merge candidate list. When the value of the motion vector ischanged, merge candidates may be added while changing the value of themotion vector in the order of (0, 0), (1, 0), (−1, 0), (0, 1), and(0,−1), for example.

Next, the inter-prediction information selecting unit 137 of theinter-prediction information deriving unit 104 of the moving picturecoding device will be described. FIG. 37 is a flowchart for describingthe flow of the process of the inter-prediction information selectingunit 137 of the inter-prediction information deriving unit 104 of themoving picture coding device. In FIG. 12 of the first practical example,in the inter-prediction information selecting unit 137 of theinter-prediction information deriving unit 104 of the moving picturecoding device, when the number of merge candidates numMergeCand islarger than 0 (step S8101 of FIG. 37: YES), a merge candidate isselected among valid merge candidates which are added to the mergecandidate list and of which the merge index is within the range of 0 to(numMergeCand−1), the inter-prediction information including the flagspredFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whether or not touse the L0 prediction and L1 prediction of the respective predictionblocks of the selected merge candidate, the reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP], and the motion vectorsmvL0[xP][yP] and mvL1[xP][yP] are supplied to the motion-compensatedprediction unit 105, and the merge index for identifying the selectedmerge candidate is supplied to the prediction method determining unit107 (step S8102 of FIG. 37). When the value of the merge index mergeIdxis smaller than the value of the number of merge candidates numMergeIdx,the merge index mergeIdx indicates a valid merge candidate added to themerge candidate list mergeCandList. When the value of the merge indexmergeIdx is larger than or equal to the value of the number of mergecandidates numMergeIdx, the merge index mergeIdx indicates an invalidmerge candidate that is not added to the merge candidate listmergeCandList. By applying rules described later to the coder side, evenwhen the merge index mergeIdx indicates an invalid merge candidate, itis possible to select a valid merge candidate.

When merge candidates are selected, the same method as that used by theprediction method determining unit 107 can be used. Coding information,a coding amount of a residual signal, and a coding distortion between aprediction picture signal and a picture signal are derived forrespective merge candidates and a merge candidate having the smallestcoding amount and coding distortion is determined. The syntax elementmerge_idx of the merge index, which is the coding information of themerge mode is entropy-coded for respective merge candidates to derive acoding amount of the coding information. Further, a coding amount of aprediction residual signal obtained by coding a prediction residualsignal between a prediction picture signal obtained by performing motioncompensation using the inter-prediction information of the mergecandidates according to the same method as the motion-compensatedprediction unit 105 for respective merge candidates and a picture signalof a coding target supplied from the picture memory 101 is derived. Atotal occurrence coding amount obtained by adding a coding amount of thecoding information (that is, the merge index) and a coding amount of theprediction residual signal is derived and used as an evaluation value.

Moreover, after such a prediction residual signal is coded, theprediction residual signal is decoded for evaluation of a distortionamount, and a coding distortion is derived as a ratio representing anerror from an original picture signal resulting from coding. The totaloccurrence coding amount and the coding distortion are compared forrespective merge candidates, whereby the coding information having thesmaller occurrence coding amount and coding distortion is determined.The merge index corresponding to the determined coding information iscoded as a flag merge_idx represented by a second syntax pattern ofprediction block units.

The occurrence coding amount derived herein is preferably obtained bysimulating the coding process but may be obtained by approximation orestimation.

On the other hand, when the number of merge candidates numMergeCand is 0(step S8102 of FIG. 37: NO), the inter-prediction information having thedefault value corresponding to the predetermined slice type is suppliedto the motion-compensated prediction unit 105 (steps S8103 to S8105).When the slice type is P-slice (step S8103 of FIG. 37: YES), the defaultvalue of the inter-prediction information is set such that L0 prediction(Pred_L0) is used (the values of the flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] are 1 and 0, respectively), the L0 reference index is0 (the values of the reference indice refIdxL0[xP][yP] andrefIdxL1[xP][yP] are 0 and −1, respectively), and the L0 vector valuemvL0[xP][yP] is (0, 0) (step S8104 of FIG. 37). On the other hand, whenthe slice type is not P-slice (step S8103: NO), (that is, the slice typeis B-slice), the default value of the inter-prediction information isset such that the inter-prediction mode is bi-prediction (Pred_BI) (bothvalues of the flags predFlagL0[xP][yP] and predFlagL1[xP][yP] are 1),both reference indice are 0 (both values of the reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP] are 0), and both the L0 and L1vector values mvL0[xP][yP] and mvL1[xP][yP] are (0, 0) (step S8105).Regardless of the slice type, even when the slice type is B-slice, thedefault value of the inter-prediction information may be set such thatL0 prediction (Pred_L0) is used (the values of the flagspredFlagL0[xP][yP] and predFlagL1[xP][yP] are 1 and 0, respectively),the L0 reference index is 0 (the values of the reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP] are 0 and −1, respectively), andthe L0 vector value mvL0[xP][yP] is (0, 0).

Next, the inter-prediction information selecting unit 237 of theinter-prediction information deriving unit 205 of the moving picturedecoding device will be described. FIG. 38 is a flowchart for describingthe flow of the process of the inter-prediction information selectingunit 237 of the inter-prediction information deriving unit 205 of themoving picture decoding device. In FIG. 13 of the first practicalexample, when the number of merge candidates numMergeCand is larger than0 (step S9101 of FIG. 38: YES), the inter-prediction informationselecting unit 237 of the inter-prediction information deriving unit 205of the moving picture decoding device selects a merge candidatecorresponding to the merge index mergeIdx supplied from the secondbitstream decoder 202 among the merge candidates added to the mergecandidate list mergeCandList, supplies the inter-prediction informationincluding the flags predFlagL0[xP][yP] and predFlagL1[xP][yP] indicatingwhether or not to use the L0 prediction and L1 prediction of theselected merge candidate, the L0 and L1 reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP], and the L0 and L1 motion vectorsmvL0[xP][yP] and mvL1[xP][yP] to the motion-compensated prediction unit206, and stores the same in the coding information storage memory 210(step S9102 of FIG. 38).

When a merge index indicating an invalid merge candidate is coded on thecoder side, an invalid merge candidate is selected on the decoder side.In this case, inter-prediction is performed using the invalidinter-prediction information and unexpected prediction signals may beobtained. Moreover, the inter-prediction mode may have a value that doesnot conform to the standards and the reference index may indicate areference picture that is not present whereby an error may occur anddecoding may end abnormally.

Thus, in the first practical example of the present embodiment, when thevalue of the supplied merge index mergeIdx is larger than or equal tothe value of the number of merge candidates numMergeIdx, the value ofthe number of merge candidates numMergeIdx is set to the merge indexmergeIdx, and then, the process is performed. When the value of thesupplied merge index mergeIdx is larger than or equal to the number ofmerge candidates numMergeIdx, the merge index mergeIdx set on the coderside indicates an invalid merge candidate that is not added to the mergecandidate list mergeCandList. By clipping the merge index mergeIdx, itis possible to obtain a merge candidate that is added last to the mergecandidate list mergeCandList. By defining the clipping process on themerge index mergeIdx, it is possible to prevent the decoder fromselecting an invalid merge candidate that is not added to the mergecandidate list mergeCandList.

Alternatively, when the value of the supplied merge index mergeIdx islarger than or equal to the number of merge candidates numMergeIdx, bysetting the inter-prediction information of the merge candidate to apredetermined value, it is possible to prevent an invalid mergecandidate from being selected. The predetermined inter-predictioninformation of the merge candidate is set such that the prediction modeis L0 prediction, the value of the reference index is 0, and the valueof the motion vector is (0, 0). In the case of B-slices, the predictionmode may be set to bi-prediction.

On the other hand, when the number of merge candidates numMergeCand is 0(step S9102 of FIG. 38: NO), the inter-prediction information having thedefault value corresponding to the predetermined slice type is suppliedto the motion-compensated prediction unit 206 and is stored in thecoding information storage memory 210 (steps S9103 to S9105 of FIG. 38).When the slice type is P-slice (step S9103 of FIG. 38: YES), the defaultvalue of the inter-prediction information is set such that L0 prediction(Pred_L0) is used (the values of the flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] are 1 and 0, respectively), the L0 reference index is0 (the values of the reference indice refIdxL0[xP][yP] andrefIdxL1[xP][yP] are 0 and −1, respectively), and the L0 vector valuemvL0[xP][yP] is (0, 0) (step S9104 of FIG. 38). On the other hand, whenthe slice type is not P-slice (step S9103 of FIG. 38: NO), (that is, theslice type is B-slice), the default value of the inter-predictioninformation is set such that the inter-prediction mode is bi-prediction(Pred_BI) (both values of the flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] are 1), both reference indice are 0 (both values ofthe reference indice refIdxL0[xP][yP] and refIdxL1[xP][yP] are 0), andboth the L0 and L1 vector values mvL0[xP][yP] and mvL1[xP][yP] are (0,0) (step S9105 of FIG. 38). Regardless of the slice type, even when theslice type is B-slice, the default value of the inter-predictioninformation may be set such that L0 prediction (Pred_L0) is used (thevalues of the flags predFlagL0[xP][yP] and predFlagL1[xP][yP] are 1 and0, respectively), the L0 reference index is 0 (the values of thereference indice refIdxL0[xP][yP] and refIdxL1[xP][yP] are 0 and −1,respectively), and the L0 vector value mvL0[xP][yP] is (0, 0).

Next, an inter-prediction information deriving method according to asecond practical example of the embodiment will be described withreference to the drawings. FIG. 28 is a diagram illustrating a detailedconfiguration of the inter-prediction information deriving unit 104 ofthe moving picture coding device illustrated in FIG. 1 according to thesecond practical example of the embodiment. FIG. 29 is a diagramillustrating a detailed configuration of the inter-predictioninformation deriving unit 205 of the moving picture decoding deviceillustrated in FIG. 2 according to the second practical example of theembodiment. The inter-prediction information deriving unit 104illustrated in FIG. 28 of the second practical example is different fromthe inter-prediction information deriving unit 104 illustrated in FIG.12 of the first practical example in that a valid merge candidatesupplementing unit 135 is added. The inter-prediction informationderiving unit 205 illustrated in FIG. 29 of the second practical exampleis different from the inter-prediction information deriving unit 205illustrated in FIG. 13 of the first practical example in that a validmerge candidate supplementing unit 235 is added. In the presentembodiment, in the moving picture coding device and the moving picturedecoding device, when the value of the largest number of mergecandidates maxNumMergeCand is 0, the merge candidate deriving processand the merge candidate list constructing process of FIG. 30 may beomitted.

FIG. 30 is a flowchart for describing the flow of a merge candidatederiving process and a merge candidate list constructing process whichare the common functions of the merge candidate list constructing unit120 of the inter-prediction information deriving unit 104 of the movingpicture coding device and the merge candidate list constructing unit 220of the inter-prediction information deriving unit 205 of the movingpicture decoding device according to the second practical example of theembodiment of the present invention. The flowchart of FIG. 30 of thesecond practical example is different from the flowchart of FIG. 15 ofthe first practical example in that a valid merge candidate derivingprocess of step S105 is added.

Similarly to the first practical example, the merge candidate listconstructing unit 130 of the inter-prediction information deriving unit104 of the moving picture coding device and the merge candidate listconstructing unit 230 of the inter-prediction information deriving unit205 of the moving picture decoding device create the merge candidatelist mergeCandList (step S100 of FIG. 30). The spatial merge candidateconstructing unit 131 of the inter-prediction information deriving unit104 of the moving picture coding device and the spatial merge candidateconstructing unit 231 of the inter-prediction information deriving unit205 of the moving picture decoding device derive spatial mergecandidates A, B, C, D, and E from the prediction blocks A, B, C, D, andE neighboring to the coding/decoding target block from the codinginformation stored in the coding information storage memory 115 of themoving picture coding device or the coding information storage memory210 of the moving picture decoding device and add the derived spatialmerge candidates to the merge candidate list mergeCandList (step S101 ofFIG. 30). The temporal merge candidate reference index deriving unit 132of the inter-prediction information deriving unit 104 of the movingpicture coding device and the temporal merge candidate reference indexderiving unit 232 of the inter-prediction information deriving unit 205of the moving picture decoding device derive the reference indice of thetemporal merge candidates from the prediction blocks neighboring to thecoding/decoding target block and supply the derived reference indice tothe temporal merge candidate deriving unit 133 of the inter-predictioninformation deriving unit 104 of the moving picture coding device andthe temporal merge candidate deriving unit 233 of the inter-predictioninformation deriving unit 205 of the moving picture decoding device(step S102 of FIG. 30). The temporal merge candidate deriving unit 133of the inter-prediction information deriving unit 104 of the movingpicture coding device and the temporal merge candidate deriving unit 233of the inter-prediction information deriving unit 205 of the movingpicture decoding device derive the temporal merge candidates frompictures of different time and add the derived temporal merge candidatesto the merge candidate list mergeCandList (step S103 of FIG. 30). Theadditional merge candidate deriving unit 134 of the inter-predictioninformation deriving unit 104 of the moving picture coding device andthe additional merge candidate deriving unit 234 of the inter-predictioninformation deriving unit 205 of the moving picture decoding devicederive additional merge candidates using the number of merge candidatesnumMergeCand added to the merge candidate list mergeCandList as thelargest number of merge candidates maxNumMergeCand when the number ofmerge candidates numMergeCand added to the merge candidate listmergeCandList is smaller than the largest number of merge candidatesmaxNumMergeCand and add the derived additional merge candidates to themerge candidate list mergeCandList (step S104 of FIG. 30). The aboveprocesses are the same as those of the first practical example.Subsequently, in the second practical example, the valid merge candidatesupplementing unit 135 and the valid merge candidate supplementing unit235 supplement a valid merge candidate to eliminate an invalid mergecandidate within a range where the merge index in the merge candidatelist is indicated by a value of 0 to (maxNumMergeCand−1) (step S105 ofFIG. 30). By eliminating the invalid merge candidate within a rangewhere the merge index has a value of 0 to (maxNumMergeCand−1), it isguaranteed that an invalid merge candidate is not selected on thedecoder side and only a valid merge candidate is selected.

A valid merge candidate deriving method which is the process of stepS105 of FIG. 30 performed by the valid merge candidate supplementingunit 135 illustrated in FIG. 28 and the valid merge candidatesupplementing unit 235 illustrated in FIG. 29 illustrated in FIG. 30 ofthe second practical example of the present embodiment will be describedin detail with reference to the flowchart of FIG. 31. FIG. 31 is aflowchart for describing the flow of the valid merge candidate derivingprocess of step S105 of FIG. 30 according to the second practicalexample of the present embodiment.

In the valid merge candidate deriving process of FIG. 31 of the secondpractical example, a plurality of merge candidates having the same valueof inter-prediction information is added to the merge candidate list inorder to add a valid merge candidate to the merge candidate list with asimple process until an invalid merge candidate is eliminated within arange where the merge index in the merge candidate list is indicated bya value of 0 to (maxNumMergeCand−1). A valid merge candidate of whichthe value of the motion vector of the inter-prediction modecorresponding to the slice type is (0, 0) is added to the mergecandidate list (steps S6101 to S6113 of FIG. 31).

First, when the number of merge candidates numMergeCand is smaller thanthe largest number of merge candidates maxNumMergeCand (step S6102 ofFIG. 31: YES), the flow proceeds to step S6103. When the number of mergecandidates numMergeCand is not smaller than the largest number of mergecandidates maxNumMergeCand (step S6102 of FIG. 31: NO), the valid mergecandidate deriving process ends.

Subsequently, when the slice type is P-slice (step S6103 of FIG. 31:YES), merge candidates of which the inter-prediction mode is L0prediction (Pred_L0), the reference index is 0, and the vector value is(0, 0) are used as the valid merge candidates. (0, 0) is set to themotion vectors mvL0Zero and mvL1Zero of the valid merge candidates (stepS6104 of FIG. 31), 0 and −1 are set to the reference indice refIdxL0Zeroand refIdxL1Zero of the valid merge candidates, respectively (step S6105of FIG. 31), and 1 and 0 are set to the flags predFlagL0Zero andpredFlagL1Zero of the valid merge candidates, respectively (step S6106of FIG. 31). Then, the flow proceeds to step S6110.

On the other hand, when the slice type is not P-slice (step S6103 ofFIG. 31: NO) (that is, when the slice type is B-slice), merge candidatesof which the inter-prediction mode is bi-prediction (Pred_BI), bothreference indice are 0, both vector values are (0, 0) are used as validmerge candidates. (0, 0) is set to the motion vectors mvL0Zero andmvL1Zero of the valid merge candidates (step S6107 of FIG. 31), thevalue of the reference index i is set to the reference indicerefIdxL0Zero and refIdxL1Zero of the valid merge candidates (step S6108of FIG. 31), and 1 is set to the flags predFlagL0Zero and predFlagL1Zeroof the valid merge candidates (step S6109 of FIG. 31). Then, the flowproceeds to step S6110.

Subsequently, the valid merge candidate is added to the position atwhich the merge index of the merge candidate list mergeCandList isindicated by the same value as numMergeCand (step S6110 of FIG. 31), andthe number of merge candidates numMergeCand is incremented by 1 (stepS6112 of FIG. 31). Then, the flow proceeds to step S6113.

The processes of steps S6102 to S6112 are repeatedly performed until thenumber of merge candidates numMergeCand reaches the largest number ofmerge candidates maxNumMergeCand (steps S6101 to S6113 of FIG. 31). Withthese processes, in the second practical example, invalid mergecandidates are eliminated within a range where the merge index in themerge candidate list is indicated by the value of 0 to(maxNumMergeCand−1).

In FIG. 28 of the second practical example, when the number of mergecandidates numMergeCand is larger than 0 (step S8101 of FIG. 37: YES),similarly to the inter-prediction information selecting unit 137 ofillustrated in FIG. 12 of the first practical example, theinter-prediction information selecting unit 137 of the inter-predictioninformation deriving unit 104 of the moving picture coding deviceselects merge candidates among the merge candidates added to the mergecandidate list, supplies the inter-prediction information including theflags predFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whether ornot to use the L0 prediction and L1 prediction of the respectiveprediction blocks of the selected merge candidate, the reference indicerefIdxL0[xP][yP] and refIdxL1[xP][yP], and the motion vectorsmvL0[xP][yP] and mvL1[xP][yP] is supplied to the motion-compensatedprediction unit 105, and the merge index for identifying the selectedmerge candidate is supplied to the prediction method determining unit107 (step S8102 of FIG. 37). However, in the second practical example,invalid merge candidates are not present in the range where the mergeindex in the merge candidate list is indicated by the value of 0 to(maxNumMergeCand−1) and all merge candidates are valid merge candidates.When the number of merge candidates numMergeCand is 0 (step S8102: NO),the inter-prediction information having the default value correspondingto the predetermined slice type is supplied to the motion-compensatedprediction unit 105 (steps S8103 to S8105).

On the other hand, in FIG. 29 of the second practical example, when thenumber of merge candidates numMergeCand is larger than 0 (step S9101 ofFIG. 38: YES), similarly to the inter-prediction information selectingunit 237 illustrated in FIG. 13 of the first practical example, theinter-prediction information selecting unit 237 of the inter-predictioninformation deriving unit 205 of the moving picture decoding deviceselects a merge candidate corresponding to the merge index mergeIdxsupplied from the second bitstream decoder 202 among the mergecandidates added to the merge candidate list mergeCandList, supplies theinter-prediction information including the flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] indicating whether or not to use the L0 predictionand L1 prediction of the selected merge candidate, the L0 and L1reference indice refIdxL0[xP][yP] and refIdxL1[xP][yP], and the L0 andL1 motion vectors mvL0[xP][yP] and mvL1[xP][yP] to themotion-compensated prediction unit 206, and stores the same in thecoding information storage memory 210. However, in the second practicalexample, invalid merge candidates are not present in the range where themerge index in the merge candidate list is indicated by the value of 0to (maxNumMergeCand−1) and all merge candidates are valid mergecandidates. On the other hand, when the number of merge candidatesnumMergeCand is 0 (step S9102 of FIG. 38: NO), the inter-predictioninformation having the default value corresponding to the predeterminedslice type is supplied to the motion-compensated prediction unit 206 andis stored in the coding information storage memory 210 (steps S9103 toS9105 of FIG. 38).

Next, an inter-prediction information deriving method according to athird practical example of the present embodiment will be described.FIG. 28 is also a diagram illustrating a detailed configuration of theinter-prediction information deriving unit 104 of the moving picturecoding device illustrated in FIG. 1 according to the third practicalexample of the embodiment. FIG. 29 is also a diagram illustrating adetailed configuration of the inter-prediction information deriving unit205 of the moving picture decoding device illustrated in FIG. 2according to the third practical example of the embodiment. FIG. 30 isalso a flowchart for describing the flow of a merge candidate derivingprocess and a merge candidate list constructing process which are thecommon functions of the merge candidate list constructing unit 120 ofthe inter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 220 of theinter-prediction information deriving unit 205 of the moving picturedecoding device according to the third practical example of theembodiment of the present invention. In the third practical example,similarly to the second practical example, the valid merge candidatesupplementing unit 135 illustrated in FIG. 28 and the valid mergecandidate supplementing unit 235 illustrated in FIG. 29 supplement validmerge candidates to eliminate invalid merge candidates within the rangewhere the merge index in the merge candidate list is indicated by thevalue of 0 to (maxNumMergeCand−1) (step S105 of FIG. 30). By eliminatingthe invalid merge candidate within a range where the merge index has avalue of 0 to (maxNumMergeCand−1), it is guaranteed that an invalidmerge candidate is not selected on the decoder side and only a validmerge candidate is selected. However, in the third practical example,regardless of the slice type, merge candidates of which theinter-prediction mode is L0 prediction (Pred_L0), the reference index is0, and the vector value is (0, 0) are used as the valid mergecandidates. The merge candidate list constructing unit 120 of theinter-prediction information deriving unit 104 of the moving picturecoding device of the second practical example illustrated in FIG. 28 andthe merge candidate list constructing unit 220 of the inter-predictioninformation deriving unit 205 of the moving picture decoding deviceillustrated in FIG. 29 have the same configuration as those of the thirdpractical example. However, the process of step S105 of FIG. 30performed by the valid merge candidate supplementing unit 135 and thevalid merge candidate supplementing unit 235 is different from that ofthe second practical example.

A valid merge candidate deriving method which is the process of stepS105 of FIG. 30 performed by the valid merge candidate supplementingunit 135 illustrated in FIG. 28 and the valid merge candidatesupplementing unit 235 illustrated in FIG. 29 of the third practicalexample of the present embodiment will be described in detail withreference to the flowchart of FIG. 32. FIG. 32 is a flowchart fordescribing the flow of the valid merge candidate deriving process ofstep S105 of FIG. 30 according to the third practical example of thepresent embodiment.

In the valid merge candidate deriving process of FIG. 32 of the thirdpractical example, similarly to the valid merge candidate derivingprocess of FIG. 31 of the second practical example, a plurality of mergecandidates having the same value of inter-prediction information isadded to the merge candidate list in order to add a valid mergecandidate to the merge candidate list with a simple process until aninvalid merge candidate is eliminated within a range where the mergeindex in the merge candidate list is indicated by a value of 0 to(maxNumMergeCand−1). However, in the third practical example, regardlessof the slice type, by setting the inter-prediction mode to L0 prediction(Pred_L0), a valid merge candidate of which the value of the motionvector of the inter-prediction mode corresponding to the slice type is(0, 0) is added to the merge candidate list (steps S6101 to S6113 ofFIG. 32).

First, when the number of merge candidates numMergeCand is smaller thanthe largest number of merge candidates maxNumMergeCand (step S6102 ofFIG. 32: YES), the flow proceeds to step S6103. When the number of mergecandidates numMergeCand is not smaller than the largest number of mergecandidates maxNumMergeCand (step S6102 of FIG. 32: NO), the valid mergecandidate deriving process ends.

Subsequently, merge candidates of which the inter-prediction mode is L0prediction (Pred_L0), the reference index is 0, and the vector value is(0, 0) are used as the valid merge candidates. (0, 0) is set to themotion vectors mvL0Zero and mvL1Zero of the valid merge candidates (stepS6104 of FIG. 32), 0 and −1 are set to the reference indice refIdxL0Zeroand refIdxL1Zero of the valid merge candidates, respectively (step S6105of FIG. 32), and 1 and 0 are set to the flags predFlagL0Zero andpredFlagL1Zero of the valid merge candidates, respectively (step S6106of FIG. 32).

Subsequently, the valid merge candidate is added to the position atwhich the merge index of the merge candidate list mergeCandList isindicated by the same value as numMergeCand (step S6110 of FIG. 32), andthe number of merge candidates numMergeCand is incremented by 1 (stepS6112 of FIG. 32). Then, the flow proceeds to step S6113.

The processes of steps S6102 to S6112 are repeatedly performed until thenumber of merge candidates numMergeCand reaches the largest number ofmerge candidates maxNumMergeCand (steps S6101 to S6113 of FIG. 32). Withthese processes, in the third practical example, invalid mergecandidates are eliminated within a range where the merge index in themerge candidate list is indicated by the value of 0 to(maxNumMergeCand−1).

Next, an inter-prediction information deriving method according to afourth practical example of the present embodiment will be described.FIG. 28 is also a diagram illustrating a detailed configuration of theinter-prediction information deriving unit 104 of the moving picturecoding device illustrated in FIG. 1 according to the fourth practicalexample of the embodiment. FIG. 29 is also a diagram illustrating adetailed configuration of the inter-prediction information deriving unit205 of the moving picture decoding device illustrated in FIG. 2according to the fourth practical example of the embodiment. FIG. 30 isalso a flowchart for describing the flow of a merge candidate derivingprocess and a merge candidate list constructing process which are thecommon functions of the merge candidate list constructing unit 120 ofthe inter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 220 of theinter-prediction information deriving unit 205 of the moving picturedecoding device according to the fourth practical example of theembodiment of the present invention. In the fourth practical example,similarly to the second and third practical examples, the valid mergecandidate supplementing unit 135 illustrated in FIG. 28 and the validmerge candidate supplementing unit 235 illustrated in FIG. 29 supplementvalid merge candidates to eliminate invalid merge candidates within therange where the merge index in the merge candidate list is indicated bythe value of 0 to (maxNumMergeCand−1) (step S105 of FIG. 30). Byeliminating the invalid merge candidate within a range where the mergeindex has a value of 0 to (maxNumMergeCand−1), it is guaranteed that aninvalid merge candidate is not selected on the decoder side and only avalid merge candidate is selected. However, in the fourth practicalexample, a merge candidate added last to the merge list is repeatedlyadded to the merge candidate list as a valid merge candidate. The mergecandidate list constructing unit 120 of the inter-prediction informationderiving unit 104 of the moving picture coding device of the second andthird practical examples illustrated in FIG. 28 and the merge candidatelist constructing unit 220 of the inter-prediction information derivingunit 205 of the moving picture decoding device illustrated in FIG. 29have the same configuration as those of the fourth practical example.However, the process of step S105 of FIG. 30 performed by the validmerge candidate supplementing unit 135 and the valid merge candidatesupplementing unit 235 is different from that of the second and thirdpractical examples.

A valid merge candidate deriving method which is the process of stepS105 of FIG. 30 performed by the valid merge candidate supplementingunit 135 illustrated in FIG. 28 and the valid merge candidatesupplementing unit 235 illustrated in FIG. 29 of the fourth practicalexample of the present embodiment will be described in detail withreference to the flowchart of FIG. 32. FIG. 33 is a flowchart fordescribing the flow of the valid merge candidate deriving process ofstep S105 of FIG. 30 according to the fourth practical example of thepresent embodiment.

In the valid merge candidate deriving process of FIG. 33 of the fourthpractical example, similarly to the valid merge candidate derivingprocess of FIGS. 31 and 32 of the second and third practical examples,respectively, a plurality of merge candidates having the same value ofinter-prediction information is added to the merge candidate list inorder to add a valid merge candidate to the merge candidate list with asimple process until an invalid merge candidate is eliminated within arange where the merge index in the merge candidate list is indicated bya value of 0 to (maxNumMergeCand−1). However, in the fourth practicalexample, a merge candidate added last to the merge list is repeatedlyadded to the merge candidate list as a valid merge candidate (stepsS6101 to S6113 of FIG. 33).

First, when the number of merge candidates numMergeCand is smaller thanthe largest number of merge candidates maxNumMergeCand (step S6102 ofFIG. 33: YES), the flow proceeds to step S6111. When the number of mergecandidates numMergeCand is not smaller than the largest number of mergecandidates maxNumMergeCand (step S6102 of FIG. 33: NO), the valid mergecandidate deriving process ends.

Subsequently, the merge candidate added last to the merge list isrepeatedly added to the merge candidate list as a valid merge candidate(step S6111 of FIG. 33). Specifically, a merge candidate of which theinter-prediction mode, the reference index, and the vector value are thesame as those of the merge candidate added at the position correspondingto the index value (numMergeIdx−1) of the merge candidate list is addedat the position at which the merge index of the merge candidate listmergeCandList is indicated by the same value as numMergeCand as thevalid merge candidate. Subsequently, the number of merge candidatesnumMergeCand is incremented by 1 (step S6112 of FIG. 33), and the flowproceeds to step S6113.

The processes of steps S6102 to S6112 are repeatedly performed until thenumber of merge candidates numMergeCand reaches the largest number ofmerge candidates maxNumMergeCand (steps S6101 to S6113 of FIG. 33). Withthese processes, in the fourth practical example, invalid mergecandidates are eliminated within a range where the merge index in themerge candidate list is indicated by the value of 0 to(maxNumMergeCand−1).

Next, an inter-prediction information deriving method according to afifth practical example of the present embodiment will be described.FIG. 28 is also a diagram illustrating a detailed configuration of theinter-prediction information deriving unit 104 of the moving picturecoding device illustrated in FIG. 1 according to the fourth practicalexample of the embodiment. FIG. 29 is also a diagram illustrating adetailed configuration of the inter-prediction information deriving unit205 of the moving picture decoding device illustrated in FIG. 2according to the fourth practical example of the embodiment. FIG. 30 isalso a flowchart for describing the flow of a merge candidate derivingprocess and a merge candidate list constructing process which are thecommon functions of the merge candidate list constructing unit 120 ofthe inter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 220 of theinter-prediction information deriving unit 205 of the moving picturedecoding device according to the fourth practical example of theembodiment of the present invention. In the fifth practical example, acombination of the additional merge candidate deriving process of FIG.26 of the fourth practical example and the valid merge candidatederiving process of FIG. 33 is performed.

An additional merge candidate and valid merge candidate deriving methodof step S110 which is a combination of steps S104 and S105 of FIG. 30,performed by an additional merge candidate and valid merge candidatederiving block 121 which a combination of the processes performed by theadditional merge candidate deriving unit 134 and the valid mergecandidate supplementing unit 135 of FIG. 28 of the fifth practicalexample and an additional merge candidate and valid merge candidatederiving block 221 which is a combination of the processes performed bythe additional merge candidate deriving unit 234 and the valid mergecandidate supplementing unit 235 of FIG. 29 will be described in detail.FIG. 34 is a flowchart for describing the flow of the additional mergecandidate and valid merge candidate deriving process of step S110 ofFIG. 30 according to the fifth practical example of the presentembodiment.

In the additional merge candidate and valid merge candidate derivingprocess of FIG. 34, a plurality of merge candidates having differentvalues of inter-prediction information is derived and added to the mergecandidate list in order to broaden the choices for merge candidates toimprove the coding efficiency. After that, a plurality of mergecandidates having the same value of inter-prediction information isadded to the merge candidate list in order to add a valid mergecandidate to the merge candidate list until an invalid merge candidateis eliminated within a range where the merge index in the list isindicated by a value of 0 to (maxNumMergeCand−1) (steps S5101 to S5119of FIG. 34).

First, when the slice type is P-slice (step S5101 of FIG. 34: YES), thevalue of the number of L0 reference indice is set to a variablenumRefIdx indicating the number of reference indice (step S5102 of FIG.34). On the other hand, when the slice type is no P-slice (step S5101 ofFIG. 34: NO), that is, when the slice type is B-slice, the smaller valueamong the number of L0 reference indice and the number of L1 referenceindice is set to the variable numRefIdx indicating the number ofreference indice (step S5103 of FIG. 34). Subsequently, 0 is set to thereference index i (step S5104 of FIG. 34).

Subsequently, an additional merge candidate of which the value of themotion vector of the prediction mode corresponding to the slice type is(0, 0) is derived while changing the reference index i and added to themerge candidate list (steps S5105 to S5119 of FIG. 34).

First, when the number of merge candidates numMergeCand is smaller thanthe largest number of merge candidates maxNumMergeCand (step S5106 ofFIG. 34: YES), the flow proceeds to step S5107. When the number of mergecandidates numMergeCand is not smaller than the largest number of mergecandidates maxNumMergeCand (step S5106 of FIG. 34: NO), the additionalmerge candidate deriving process ends.

Subsequently, when the reference index i is smaller than the variablenumRefIdx (step S5107 of FIG. 34: YES), the flow proceeds to step S5109and an additional merge candidate adding process is performed. When thereference index i is not smaller than the variable numRefIdx (step S5107of FIG. 34: NO), (numRefIdx−1) is set to the reference index i (stepS5108 of FIG. 34), the flow proceeds to step S5109, and a valid mergecandidate adding process is performed.

Subsequently, when the slice type is P-slice (step S5109 of FIG. 34:YES), (0, 0) is set to the motion vectors mvL0Zero and mvL1Zero of theadditional merge candidates (step S5110 of FIG. 34), the value of thereference index i and −1 are set to the reference indice refIdxL0Zeroand refIdxL1Zero of the additional merge candidates, respectively (stepS5111 of FIG. 34), and 1 and 0 are set to the flags predFlagL0Zero andpredFlagL1Zero of the additional merge candidates, respectively (stepS5112 of FIG. 34). Then, the flow proceeds to step S5116.

On the other hand, when the slice type is not P-slice (step S5109 ofFIG. 34: NO) (that is, when the slice type is B-slice), (0, 0) is set tothe motion vectors mvL0Zero and mvL1Zero (step S5113 of FIG. 34), thevalue of the reference index i is set to the reference indicerefIdxL0Zero and refIdxL1Zero of the additional merge candidates (stepS5114 of FIG. 34), and 1 is set to the flags predFlagL0Zero andpredFlagL1Zero of the additional merge candidates (step S5115 of FIG.34). Then, the flow proceeds to step S5116.

Subsequently, the additional merge candidate is added to the position atwhich the merge index of the merge candidate list mergeCandList isindicated by the same value as numMergeCand (step S5116 of FIG. 34), andthe number of merge candidates numMergeCand is incremented by 1 (stepS5117 of FIG. 34). Subsequently, the index i is incremented by 1 (stepS5118 of FIG. 34), and the flow proceeds to step S5119.

The processes of steps S5106 to S5118 are repeatedly performed forrespective reference indice i (steps S5105 to S5119 of FIG. 34). Withthese processes, in the fifth practical example, invalid mergecandidates are eliminated within a range where the merge index in themerge candidate list is indicated by the value of 0 to(maxNumMergeCand−1).

Next, an inter-prediction information deriving method according to asixth practical example of the present embodiment will be described.FIG. 28 is also a diagram illustrating a detailed configuration of theinter-prediction information deriving unit 104 of the moving picturecoding device illustrated in FIG. 1 according to the sixth practicalexample of the embodiment. FIG. 29 is also a diagram illustrating adetailed configuration of the inter-prediction information deriving unit205 of the moving picture decoding device illustrated in FIG. 2according to the sixth practical example of the embodiment. FIG. 30 isalso a flowchart for describing the flow of a merge candidate derivingprocess and a merge candidate list constructing process which are thecommon functions of the merge candidate list constructing unit 120 ofthe inter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 220 of theinter-prediction information deriving unit 205 of the moving picturedecoding device according to the sixth practical example of theembodiment of the present invention. Although an implementation methodof the sixth practical example is different from that of the secondpractical example, the same inter-prediction information can be obtainedon the decoder side. In the sixth practical example, inter-predictioninformation within the range of all indice in the merge candidate listor where the index is indicated by the value of 0 to (maxMergeCand−1) isinitialized to a predetermined value, and the process of deriving andadding respective merge candidates is performed. When the slice type isP-slice, the merge candidate list constructing unit 130 of FIG. 28 andthe merge candidate list constructing unit 230 of FIG. 29 initialize allelements in the merge candidate list by setting the inter-predictionmode to L0 prediction (Pred_L0), the reference index to 0, and thevector value to (0, 0). When the slice type is not P-slice (that is, theslice type is B-slice), all elements in the merge candidate list areinitialized by setting the inter-prediction mode to bi-prediction(Pred_BI), both reference indice to 0, and both vector values to (0, 0).Further, 0 is set to the number of merge candidates numMergeCand.

Further, the valid merge candidate supplementing unit 135 of FIG. 29 andthe valid merge candidate supplementing unit 235 of FIG. 30 according tothe sixth practical example make the initialized inter-predictioninformation valid so that the merge candidates are used as valid mergecandidate. A valid merge candidate deriving method which is the processof step S105 of FIG. 30 performed by the valid merge candidatesupplementing unit 135 illustrated in FIG. 28 and the valid mergecandidate supplementing unit 235 illustrated in FIG. 29 of the sixthpractical example of the present embodiment will be described in detailwith reference to the flowchart of FIG. 35. FIG. 35 is a flowchart fordescribing the flow of the process of making the initializedinter-prediction information valid as valid merge candidates of stepS105 of FIG. 30 according to the sixth practical example of the presentembodiment. When the number of merge candidates numMergeCand is smallerthan the largest number of merge candidates maxNumMergeCand (step S6201of FIG. 35), the value of the largest number of merge candidatesmaxNumMergeCand is set to the number of merge candidates numMergeCand(step S6201 of FIG. 35). With this process, the merge candidate listconstructing unit 130 of FIG. 29 and the merge candidate listconstructing unit 230 of FIG. 30 make the initialized inter-predictioninformation valid so that the merge candidates are used as valid mergecandidates.

Next, an inter-prediction information deriving method according to aseventh practical example of the present embodiment will be described.FIG. 28 is also a diagram illustrating a detailed configuration of theinter-prediction information deriving unit 104 of the moving picturecoding device illustrated in FIG. 1 according to the seventh practicalexample of the embodiment. FIG. 29 is also a diagram illustrating adetailed configuration of the inter-prediction information deriving unit205 of the moving picture decoding device illustrated in FIG. 2according to the seventh practical example of the embodiment. FIG. 30 isalso a flowchart for describing the flow of a merge candidate derivingprocess and a merge candidate list constructing process which are thecommon functions of the merge candidate list constructing unit 120 ofthe inter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 220 of theinter-prediction information deriving unit 205 of the moving picturedecoding device according to the seventh practical example of theembodiment of the present invention. Although an implementation methodof the seventh practical example is different from that of the thirdpractical example, the same inter-prediction information can be obtainedon the decoder side. In the seventh practical example, similarly to thesixth practical example, inter-prediction information within the rangeof all indice in the merge candidate list or where the index isindicated by the value of 0 to (maxMergeCand−1) is initialized to apredetermined value, and the process of deriving and adding respectivemerge candidates is performed. However, in the seventh practicalexample, the merge candidate list constructing unit 130 of FIG. 28 andthe merge candidate list constructing unit 230 of FIG. 29 initialize allelements in the merge candidate list by setting the inter-predictionmode to L0 prediction (Pred_L0), the reference index to 0, and thevector value to (0, 0) regardless of the slice type. The other processesare the same as those of the sixth practical example.

Hereinabove, the present embodiment has been described. When a mergeindex indicating an invalid merge candidate is coded on the coder side,an invalid merge candidate is selected on the decoder side. In thiscase, inter-prediction is performed using the invalid inter-predictioninformation and unexpected prediction signals may be obtained. Moreover,the inter-prediction mode may have a value that does not conform to thestandards and the reference index may indicate a reference picture thatis not present whereby an error may occur and decoding may endabnormally.

According to the first practical example of the present embodiment, evenwhen a merge index indicating an invalid merge candidate is coded on thecoder side, inter-prediction using the inter-prediction information ofthe invalid merge candidate will not be performed on the decoder side.Since the moving picture coding device according to the rules of thepresent embodiment can obtain the same inter-prediction information andthe same prediction signal, it is possible to obtain the same decodedpicture.

According to the second to seventh practical examples of the presentembodiment, the merge index indicating an invalid merge candidate willnot be selected and coded on the coder side, and it is guaranteed thatinter-prediction using the inter-prediction information of the invalidmerge candidate is not performed on the decoder side. Since the movingpicture decoding device can obtain the same inter-prediction informationand the same prediction signal, it is possible to obtain the samedecoded picture.

According to the second to fifth practical examples of the presentembodiment, the valid merge candidate supplementing unit 135 of themoving picture coding device and the valid merge candidate supplementingunit 235 of the moving picture decoding device add valid mergecandidates until an invalid merge candidate is eliminated within therange where the merge index in the merge candidate list is indicated bythe value of 0 to (maxNumMergeCand−1). However, valid merge candidatesmay be added up to a predetermined range of (maxNumMergeCand−1) or moreas long as the invalid merge candidate is not present at least in therange of 0 to (maxNumMergeCand−1).

According to the sixth and seventh practical examples of the presentembodiment, the merge candidate list constructing unit 120 of theinter-prediction information deriving unit 104 of the moving picturecoding device and the merge candidate list constructing unit 220 of theinter-prediction information deriving unit 205 of the moving picturedecoding device initialize the inter-prediction information in the rangewhere the merge index in the merge candidate list is indicated by thevalue of 0 to (maxNumMergeCand−1) to the predetermined value. However,the inter-prediction information at least in the range of 0 to(maxNumMergeCand−1) may be initialized, and the inter-predictioninformation up to a predetermined range of (maxNumMergeCand−1) or moremay be initialized.

In the embodiment described above, the spatial merge candidate, thetemporal merge candidate, and the additional merge candidate arederived. However, an embodiment in which the respective merge candidatederiving processes are omitted is also included in the presentinvention. Moreover, an embodiment in which the respective mergecandidate deriving processes are modified or a new merge candidatederiving process is added is also included in the present invention.

When the additional merge candidate deriving process of FIG. 26described in the present embodiment is performed, if the slice type isB-slice, the method of the third and seventh practical examples in whicha valid merge candidate of L0 prediction having a different value ofinter-prediction information from the additional merge candidate issupplemented is more suitable than the method of the second and sixthpractical examples in which a valid merge candidate having the samevalue of inter-prediction information as the additional merge candidateis supplemented. When the additional merge candidate deriving process ofFIG. 26 described in the present embodiment is not performed, if theslice type is B-slice, the method of the second and sixth practicalexamples in which a valid merge candidate of bi-prediction having highprediction efficiency is supplemented is more suitable than the methodof the third and seventh practical examples in which a valid mergecandidate of L0 prediction is supplemented.

When the value of the largest number of merge candidates maxNumMergeCandis 0, the inter-prediction information having the default value is notdefined, and the skip mode and the merge mode are inhibited, althoughthe flags of the skip mode and merge mode are transmitted, codingefficiency decreases because the skip mode or the merge mode cannot beselected. Further, when the skip mode or the skip mode which isinhibited on the coder side is selected and a coded bitstream isdecoded, an error occurs on the decoder side, and the decoding processmay end abnormally.

However, in the present embodiment, regardless of the value of thelargest number of merge candidates maxNumMergeCand, the merge modeincluding the skip mode can always be selected when the value of thelargest number of merge candidates maxNumMergeCand is 0. In this case,in the skip mode or the movable range, the inter-prediction informationhaving the default value is output. As an example of the default valueof the inter-prediction information, when the slice type is B-slice, thedefault value is defined such that the prediction mode is bi-prediction(Pred_BI), the value of the reference picture index is 0, and the valueof the motion vector is (0, 0). Thus, even when the value of the largestnumber of merge candidates maxNumMergeCand is 0, it is guaranteed thatcoding is not performed on the coder side with the skip mode or themerge mode as an invalid value and that inter-prediction using theinter-prediction information having the predetermined default value isperformed on the decoder side. Thus, since the moving picture decodingdevice can obtain the same inter-prediction information and the sameprediction signal, it is possible to obtain the same decoded picture.Further, even when the value of the largest number of merge candidatesmaxNumMergeCand is 0, since the skip mode or the merge mode can beselected, coding efficiency is improved as compared to when the skipmode or the merge mode is inhibited.

When the value of the largest number of merge candidates maxNumMergeCandis 0, the inter-prediction information of the merge mode including theskip mode uses the default value, it is not necessary to perform themerge candidate list constructing process unlike the case where thevalue of the largest number of merge candidates maxNumMergeCand islarger than or equal to 1. Thus, it is possible to realize a codingdevice which does not perform the merge candidate list constructingprocess and has a small processing amount. Moreover, since the processon the decoder side involves setting the default value to theinter-prediction information of the merge mode including the skip modeonly, it is possible to minimize the processing amount on the decoderside and to cope with a decoding device capable of suppressing adecrease in the coding efficiency.

The bitstream of the moving picture output by the moving picture codingdevice according to the embodiment has a specific data format that canbe decoded according to a coding method used in the embodiment, and themoving picture decoding device corresponding to the moving picturecoding device can decode the bitstream having the specific data format.

When a wired or wireless network is used to exchange the bitstreambetween the moving picture coding device and the moving picture decodingdevice, the bitstream may be converted to have a data format appropriatefor a transmission form of a communication path and then transmitted. Inthis case, a moving picture transmitter that converts the bitstreamoutput by the moving picture coding device into coding data having thedata format appropriate for a transmission form of a transmission pathand then transmits the coding data to the network and a moving picturereceiver that receives the coding data from the network, reconstructsthe bitstream, and supplies the reconstructed bitstream to the movingpicture decoding device are provided.

The moving picture transmitter includes a memory that buffers thebitstream output by the moving picture coding device, a packetprocessing unit that packetizes the bitstream, and a transmitting unitthat transmits the packetized coding data via the network. The movingpicture receiver includes a receiving unit that receives the packetizedcoding data via the network, a memory that buffers the received codingdata, and a packet processing unit that performs packet processing onthe coding data to construct the bitstream, and provides the constructedbitstream to the moving picture decoding device.

The process related to coding and decoding described above may beimplemented as transmitting, accumulating, and receivers using hardware,and may be implemented by firmware stored in a read only memory (ROM), aflash memory, or the like or software of a computer or the like. Afirmware program and a software program may be recorded in a computerreadable recording medium and provided, may be provided from a servervia a wired or wireless network, or may be provided as data broadcastingof digital terrestrial or satellite broadcasting.

The embodiment of the present invention has been described above. Theembodiment is an example, and a person skilled in the art may understandthat various modifications or changes on a combination of respectiveconstituent components and processing processes can be made and suchmodifications or changes fall within the scope of the invention.

[Item 1]

A moving picture coding device that codes moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information coding unit that codes information indicating adesignated number of inter-prediction information candidates;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the coding target prediction block using theselected inter-prediction information candidate.

[Item 2]

A moving picture coding device that codes moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information coding unit that codes information indicating adesignated number of inter-prediction information candidates;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list and that derives one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adds thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe additionally added inter-prediction information candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the coding target prediction block using theselected inter-prediction information candidate.

[Item 3]

A moving picture coding device that codes a bitstream obtained by codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures,comprising:

a prediction information coding unit that codes information indicating adesignated number of inter-prediction information candidates;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, that derives one or aplurality of inter-prediction information candidates of which theprediction mode and the motion vector have the same value as and thereference index is changed from that of the inter-prediction informationcandidates having the predetermined value when the number ofinter-prediction information candidates included in the addedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe added inter-prediction information candidate list, and that derivesinter-prediction information candidates of which the prediction mode,the reference index, and the motion vector have predetermined valuesuntil the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate listreaches the designated number of inter-prediction information candidateswhen the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate list issmaller than the designated number of inter-prediction informationcandidates and additionally adds the derived inter-predictioninformation candidates to the additionally added inter-predictioninformation candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the coding target prediction block using theselected inter-prediction information candidate.

[Item 4]

The moving picture coding device according to any one of items 1 to 3,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of a prediction mode corresponding to a slice type.

[Item 5]

The moving picture coding device according to any one of items 1 to 3,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of which the prediction mode is bi-prediction for B-slices ofthe picture and is L0 prediction for P-slices of the picture.

[Item 6]

The moving picture coding device according to any one of items 1 to 3,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of which the value of the reference index is 0.

[Item 7]

The moving picture coding device according to any one of items 1 to 3,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of which the value of the motion vector is (0, 0).

[Item 8]

A moving picture coding device that codes moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information deriving unit that stores and initializes adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, derives inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the coding target prediction block using theselected inter-prediction information candidate.

[Item 9]

A moving picture coding device that codes moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information coding unit that codes information indicating adesignated number of inter-prediction information candidates;

a prediction information deriving unit that derives inter-predictioninformation candidates based on the number of candidates designated asthe number of inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforms inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate and that performsinter-prediction on the coding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

[Item 10]

A moving picture coding device that codes moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information deriving unit that derives inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate supplementing unit that supplements inter-predictioninformation candidates having the same prediction mode, reference index,and motion vector until the number of inter-prediction informationcandidates reaches the designated number of candidates when the numberof inter-prediction information candidates is smaller than thedesignated number of candidates; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesand performs inter-prediction on the coding target prediction blockusing the selected inter-prediction information candidate.

[Item 11]

A moving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information coding step of coding information indicating adesignated number of inter-prediction information candidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 12]

A moving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 13]

A moving picture coding method of coding a bitstream obtained by codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures,comprising:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, deriving one or a pluralityof inter-prediction information candidates of which the prediction modeand the motion vector have the same value as and the reference index ischanged from that of the inter-prediction information candidates havingthe predetermined value when the number of inter-prediction informationcandidates included in the added inter-prediction information candidatelist is smaller than the designated number of inter-predictioninformation candidates and additionally adds the derivedinter-prediction information candidates to the added inter-predictioninformation candidate list, and deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 14]

A moving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information deriving step of storing and initializing adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, deriving inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 15]

A moving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving inter-predictioninformation candidates based on the number of candidates designated asthe number of inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforming inter-prediction of the coding target prediction block usingthe selected inter-prediction information candidate and performinginter-prediction on the coding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

[Item 16]

A moving picture coding program of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, causing a computer toexecute:

a prediction information coding step of coding information indicating adesignated number of inter-prediction information candidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 17]

A moving picture coding program of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, causing a computer toexecute:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 18]

A moving picture coding program of coding a bitstream obtained by codingmoving pictures using motion-compensated prediction in units of blocksobtained by partitioning each picture of the moving pictures, causing acomputer to execute:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, deriving one or a pluralityof inter-prediction information candidates of which the prediction modeand the motion vector have the same value as and the reference index ischanged from that of the inter-prediction information candidates havingthe predetermined value when the number of inter-prediction informationcandidates included in the added inter-prediction information candidatelist is smaller than the designated number of inter-predictioninformation candidates and additionally adds the derivedinter-prediction information candidates to the added inter-predictioninformation candidate list, and deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 19]

A moving picture coding program of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, causing a computer toexecute:

a prediction information deriving step of storing and initializing adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, deriving inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 20]

A moving picture coding program of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, causing a computer toexecute:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving inter-predictioninformation candidates based on the number of candidates designated asthe number of inter-prediction information candidates frominter-prediction information of a prediction block neighboring to acoding target prediction block or a prediction block present at the sameposition as or near the coding target prediction block in a codedpicture at a temporally different position from the coding targetprediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate and performinginter-prediction on the coding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

[Item 21]

A transmitter comprising:

a packet processor that packetizes a bitstream coded according to amoving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures to obtain thepacketized bitstream; and

a transmitting unit that transmits the packetized bitstream, the movingpicture coding method comprising:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 22]

A transmission method comprising:

a packet processing step of packetizing a bitstream coded according to amoving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures to obtain thepacketized bitstream; and

a transmitting step of transmitting the packetized bitstream, the movingpicture coding method comprising:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 23]

A transmission program for causing a computer to execute:

a packet processing step of packetizing a bitstream coded according to amoving picture coding method of coding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures to obtain thepacketized bitstream; and

a transmitting step of transmitting the packetized bitstream, the movingpicture coding method comprising:

a prediction information number coding step of coding informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a coding target prediction block or a predictionblock present at the same position as or near the coding targetprediction block in a coded picture at a temporally different positionfrom the coding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the coding target prediction block usingthe selected inter-prediction information candidate.

[Item 24]

A moving picture decoding device that decodes a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information decoding unit that decodes informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

[Item 25]

A moving picture decoding device that decodes a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information decoding unit that decodes informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list and that derives one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adds thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe additionally added inter-prediction information candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

[Item 26]

A moving picture decoding device that decodes a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information decoding unit that decodes informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, that derives one or aplurality of inter-prediction information candidates of which theprediction mode and the motion vector have the same value as and thereference index is changed from that of the inter-prediction informationcandidates having the predetermined value when the number ofinter-prediction information candidates included in the addedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe added inter-prediction information candidate list, and that derivesinter-prediction information candidates of which the prediction mode,the reference index, and the motion vector have predetermined valuesuntil the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate listreaches the designated number of inter-prediction information candidateswhen the number of inter-prediction information candidates included inthe additionally added inter-prediction information candidate list issmaller than the designated number of inter-prediction informationcandidates and additionally adds the derived inter-predictioninformation candidates to the additionally added inter-predictioninformation candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

[Item 27]

The moving picture coding device according to any one of items 24 to 26,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of a prediction mode corresponding to a slice type.

[Item 28]

The moving picture coding device according to any one of items 24 to 26,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of which the prediction mode is bi-prediction for B-slices ofthe picture and is L0 prediction for P-slices of the picture.

[Item 29]

The moving picture coding device according to any one of items 24 to 26,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of which the value of the reference index is 0.

[Item 30]

The moving picture coding device according to any one of items 24 to 26,wherein

the candidate supplementing unit adds an inter-prediction informationcandidate of which the value of the motion vector is (0, 0).

[Item 31]

A moving picture decoding device that decodes a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information decoding unit that a designated number ofinter-prediction information candidates;

a prediction information deriving unit that stores and initializes adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, derives inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

[Item 32]

A moving picture decoding device that decodes moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information decoding unit that decodes informationindicating a designated number of inter-prediction informationcandidates;

a prediction information deriving unit that derives inter-predictioninformation candidates based on the number of candidates designated asthe number of inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforms inter-prediction on the decoding target prediction block usingthe selected inter-prediction information candidate and that performsinter-prediction on the decoding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

[Item 33]

A moving picture decoding device that decodes a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information deriving unit that derives inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate supplementing unit that supplements inter-predictioninformation candidates having the same prediction mode, reference index,and motion vector until the number of inter-prediction informationcandidates reaches the designated number of candidates when the numberof inter-prediction information candidates is smaller than thedesignated number of candidates; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesand performs inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 34]

A moving picture decoding method of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information decoding step of coding information indicatinga previously designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 35]

A moving picture decoding method of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 36]

A moving picture decoding method of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, deriving one or a pluralityof inter-prediction information candidates of which the prediction modeand the motion vector have the same value as and the reference index ischanged from that of the inter-prediction information candidates havingthe predetermined value when the number of inter-prediction informationcandidates included in the added inter-prediction information candidatelist is smaller than the designated number of inter-predictioninformation candidates and additionally adds the derivedinter-prediction information candidates to the added inter-predictioninformation candidate list, and deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 37]

A moving picture decoding method of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,comprising:

a prediction information number decoding step of decoding a designatednumber of inter-prediction information candidates;

a prediction information deriving step of storing and initializing adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, deriving inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 38]

A moving picture decoding method of decoding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, comprising:

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving step of deriving inter-predictioninformation candidates based on the number of candidates designated asthe number of inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforming inter-prediction of the decoding target prediction blockusing the selected inter-prediction information candidate and performinginter-prediction of the decoding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

[Item 39]

A moving picture decoding program of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,causing a computer to execute:

a prediction information decoding step of coding information indicatinga previously designated number of inter-prediction informationcandidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the inter-predictioninformation candidate list reaches the designated number ofinter-prediction information candidates when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 40]

A moving picture decoding program of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,causing a computer to execute:

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 41]

A moving picture decoding program of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,causing a computer to execute:

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, deriving one or a pluralityof inter-prediction information candidates of which the prediction modeand the motion vector have the same value as and the reference index ischanged from that of the inter-prediction information candidates havingthe predetermined value when the number of inter-prediction informationcandidates included in the added inter-prediction information candidatelist is smaller than the designated number of inter-predictioninformation candidates and additionally adds the derivedinter-prediction information candidates to the added inter-predictioninformation candidate list, and deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 42]

A moving picture decoding program of decoding a bitstream obtained bycoding moving pictures using motion-compensated prediction in units ofblocks obtained by partitioning each picture of the moving pictures,causing a computer to execute:

a prediction information number decoding step of decoding a designatednumber of inter-prediction information candidates;

a prediction information deriving step of storing and initializing adesignated number of inter-prediction information candidates havingpredetermined prediction mode, reference index, and motion vector inadvance in an inter-prediction information candidate list in which thedesignated number of inter-prediction information candidates are stored,and then, deriving inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 43]

A moving picture decoding program of decoding moving pictures usingmotion-compensated prediction in units of blocks obtained bypartitioning each picture of the moving pictures, causing a computer toexecute:

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates;

a prediction information deriving step of deriving inter-predictioninformation candidates based on the number of candidates designated asthe number of inter-prediction information candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block;

a candidate list constructing step of constructing an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates; and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from inter-prediction information candidatesincluded in the inter-prediction information candidate list when thedesignated number of candidates is larger than or equal to 1 andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate and performinginter-prediction on the decoding target prediction block usinginter-prediction information having a predetermined value when thedesignated number of candidates is 0.

[Item 44]

A receiver that receives and decodes a bitstream obtained by codingmoving pictures, comprising:

a receiving unit that receives a bitstream obtained by packetizing abitstream obtained by coding moving pictures using motion-compensatedprediction in units of blocks obtained by partitioning each picture ofthe moving pictures;

a reconstructing unit that packetizing the received bitstream toreconstruct an original bitstream;

a prediction information decoding unit that decodes informationindicating a previously designated number of inter-predictioninformation candidates from the reconstructed bitstream;

a prediction information deriving unit that derives the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addsthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list and that derives one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adds thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing unit that derives inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adds the derived inter-prediction information candidates tothe additionally added inter-prediction information candidate list; and

a motion-compensated prediction unit that selects one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list and performsinter-prediction on the decoding target prediction block using theselected inter-prediction information candidate.

[Item 45]

A reception method of receiving and decoding a bitstream obtained bycoding moving pictures, comprising:

a receiving step of receiving a bitstream obtained by packetizing abitstream obtained by coding moving pictures using motion-compensatedprediction in units of blocks obtained by partitioning each picture ofthe moving pictures;

a reconstructing step of packetizing the received bitstream toreconstruct an original bitstream;

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates from the reconstructed bitstream;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

[Item 46]

A reception program of receiving and decoding a bitstream obtained bycoding moving pictures, causing a computer to execute:

a receiving step of receiving a bitstream obtained by packetizing abitstream obtained by coding moving pictures using motion-compensatedprediction in units of blocks obtained by partitioning each picture ofthe moving pictures;

a reconstructing step of packetizing the received bitstream toreconstruct an original bitstream;

a prediction information number decoding step of decoding informationindicating a previously designated number of inter-predictioninformation candidates from the reconstructed bitstream;

a prediction information deriving step of deriving the inter-predictioninformation candidates from inter-prediction information of a predictionblock neighboring to a decoding target prediction block or a predictionblock present at the same position as or near the decoding targetprediction block in a decoded picture at a temporally different positionfrom the decoding target prediction block;

a candidate list constructing unit that constructs an inter-predictioninformation candidate list from the derived inter-prediction informationcandidates;

a candidate adding step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values when the number ofinter-prediction information candidates included in the constructedinter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates and addingthe derived inter-prediction information candidates to the constructedinter-prediction information candidate list, and deriving one or aplurality of inter-prediction information candidates of which at leastone of the prediction mode, the reference index, and the motion vectoris changed from that of the inter-prediction information candidateshaving the predetermined value when the number of inter-predictioninformation candidates included in the added inter-predictioninformation candidate list is smaller than the designated number ofinter-prediction information candidates and additionally adding thederived inter-prediction information candidates to the addedinter-prediction information candidate list;

a candidate supplementing step of deriving inter-prediction informationcandidates of which the prediction mode, the reference index, and themotion vector have predetermined values until the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list reaches the designatednumber of inter-prediction information candidates when the number ofinter-prediction information candidates included in the additionallyadded inter-prediction information candidate list is smaller than thedesignated number of inter-prediction information candidates andadditionally adding the derived inter-prediction information candidatesto the additionally added inter-prediction information candidate list;and

a motion-compensated prediction step of selecting one inter-predictioninformation candidate from the inter-prediction information candidatesincluded in the inter-prediction information candidate list andperforming inter-prediction on the decoding target prediction blockusing the selected inter-prediction information candidate.

What is claimed is:
 1. A moving picture decoding device that decodes abitstream obtained by coding moving pictures using inter-predictionbased on inter-prediction information of a merge candidate in units ofblocks obtained by partitioning each picture of the moving pictures,comprising: a prediction information decoding unit that decodesinformation indicating a designated number of merge candidates; aprediction information deriving unit that derives merge candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; a candidate list constructing unit thatconstructs a merge candidate list from the derived merge candidates; afirst candidate supplementing unit that repeatedly performs a firstprocess for adding to the merge candidate list a merge candidate ofwhich the moving vector has a first value, the inter-prediction mode hasa second value and the reference index has a third value; a secondcandidate supplementing unit that repeatedly performs a second processfor adding to the merge candidate list after the first process a mergecandidate of which the motion vector has the first value, theinter-prediction mode has the second value and the reference index has afourth value until the number of merge candidates included in the mergecandidate list after the first process reaches the designated number ofmerge candidates when the number of merge candidates included in themerge candidate list after the first process is smaller than thedesignated number of merge candidates; and a merge candidate selectingunit that selects one merge candidate from the merge candidates includedin the merge candidate list of which the number of merge candidatesreaches the designated number of merge candidates, wherein: the firstvalue is a predefined value that does not differ each time the firstprocess and the second process occur; the second value is a predefinedvalue that does not differ each time the first process and the secondprocess occur and indicates that the inter-prediction mode is L0prediction when a decoding target image is a P picture; the third valueis a variable that differs each time the first process occurs; and thefourth value is a predefined value that does not differ each time thesecond process occurs.
 2. A moving picture decoding method of decoding abitstream obtained by coding moving pictures using inter-predictionbased on inter-prediction information of a merge candidate in units ofblocks obtained by partitioning each picture of the moving pictures,comprising: a prediction information decoding step of decodinginformation indicating a designated number of merge candidates; aprediction information deriving step of deriving merge candidates frominter-prediction information of a prediction block neighboring to adecoding target prediction block or a prediction block present at thesame position as or near the decoding target prediction block in adecoded picture at a temporally different position from the decodingtarget prediction block; a candidate list constructing step ofconstructing a merge candidate list from the derived merge candidates; afirst candidate supplementing step of repeatedly performing a firstprocess for adding to the merge candidate list a merge candidate ofwhich the moving vector has a first value, the inter-prediction mode hasa second value and the reference index has a third value; a secondcandidate supplementing step of repeatedly performing a second processfor adding to the merge candidate list after the first process a mergecandidate of which the motion vector has the first value, theinter-prediction mode has the second value and the reference index has afourth value until the number of merge candidates included in the mergecandidate list after the first process reaches the designated number ofmerge candidates when the number of merge candidates included in themerge candidate list after the first process is smaller than thedesignated number of merge candidates; and a merge candidate selectingstep of selecting one merge candidate from the merge candidates includedin the merge candidate list of which the number of merge candidatesreaches the designated number of merge candidates, wherein: the firstvalue is a predefined value that does not differ each time the firstprocess and the second process occur; the second value is a predefinedvalue that does not differ each time the first process and the secondprocess occur and indicates that the inter-prediction mode is L0prediction when a decoding target image is a P picture; the third valueis a variable that differs each time the first process occurs; and thefourth value is a predefined value that does not differ each time thesecond process occurs.
 3. A non-transitory computer-readable recordingmedium having embodied thereon a moving picture decoding program ofdecoding a bitstream obtained by coding moving pictures usinginter-prediction based on inter-prediction information of a mergecandidate in units of blocks obtained by partitioning each picture ofthe moving pictures, causing a computer to execute: a predictioninformation decoding step of decoding information indicating adesignated number of merge candidates; a prediction information derivingstep of deriving merge candidates from inter-prediction information of aprediction block neighboring to a decoding target prediction block or aprediction block present at the same position as or near the decodingtarget prediction block in a decoded picture at a temporally differentposition from the decoding target prediction block; a candidate listconstructing step of constructing a merge candidate list from thederived merge candidates; a first candidate supplementing step ofrepeatedly performing a first process for adding to the merge candidatelist a merge candidate of which the moving vector has a first value, theinter-prediction mode has a second value and the reference index has athird value; a second candidate supplementing step of repeatedlyperforming a second process for adding to the merge candidate list afterthe first process a merge candidate of which the motion vector has thefirst value, the inter-prediction mode has the second value and thereference index has a fourth value until the number of merge candidatesincluded in the merge candidate list after the first process reaches thedesignated number of merge candidates when the number of mergecandidates included in the merge candidate list after the first processis smaller than the designated number of merge candidates; and a mergecandidate selecting step of selecting one merge candidate from the mergecandidates included in the merge candidate list of which the number ofmerge candidates reaches the designated number of merge candidates,wherein: the first value is a predefined value that does not differ eachtime the first process and the second process occur; the second value isa predefined value that does not differ each time the first process andthe second process occur and indicates that the inter-prediction mode isL0 prediction when a decoding target image is a P picture; the thirdvalue is a variable that differs each time the first process occurs; andthe fourth value is a predefined value that does not differ each timethe second process occurs.